Interestingly Zidane was accommodated for the same reasons during his career. Lippi played a 4-3-3 which followed the same blueprint in midfield and attack as Klopp has run with over the last decade. With Zidane in the mix, he dropped an attacker and played a 4-3-1-2. France accommodated him in a similar way, adopting a 4-3-2-1 shape for 1998 where everyone worked (even Zidane). I don't think he ever operated in a traditional flat 4-4-2. It only really became imbalanced at Real in the 2000s when they started loading up with Galacticos, which is no different really to where PSG have come unstuck in recent years. The importance of midfield and pressing from the front are obviously big parts of the modern game, but they were key in the 1990s in Serie A and international football and Zidane's career demonstrates that.
Today I imagine Zidane would enjoy playing for a superclub. He'd be higher up the park, more able to decide league games, instead of bogged down in midfield battles around the centre circle. He'd have wide players on both sides to hit that would also open up space for him in a way he never consistently benefited from during his own career. They'd have the squad depth to rotate him out for a break every few weeks.
Lippi has some interesting comments on pressing. One of the more blunt was something along the lines of "everybody presses nowadays" when discussing italian football. 90s Italian football was heavily influenced by Sacchi's Milan and the way the 88 ussr team had put their national team out of the Euro. More organised styles of pressing than " get out there and give 'em no space lads" was quite widely understood as a concept by the 90s, it just didn't proliferate to the point across leagues of being a dominant foundational thing because football was less globalised. I saw a thread on the rec.sport.soccer discussion group from about 98/99 or so, where there was debate about Italian vs Spanish league: the idea that one big tactical reason the Italians had been better over the decade was because they had more clubs that were good at pressing intelligently was quite prominent.
The bar is higher today than in the past.
In the 90s you only needed to be good enough technically. Today, you need to be good technically AND athletically. Not every technician has the capacity to do the latter, even when they try their best. Just look at some of some of the kids who graduated from our academy and failed to break into top level football despite working hard, and having more talent than bigger and stronger colleagues. Or maybe even the likes of VdB and Kagawa if you want to look at senior players.
This is too extreme. Every generation had its dividing line between players that were dedicated enough overall athletes with the necessary balance of physical and technical qualities, and the "he was a gifted natural footballer but just didn't live the lifestyle/have the athleticism" types. By the latter i don't mean high level players that eventually wasted potential by being ill-disciplined, just people that ended up playing in their countries lower-tiers because of their lifestyle/athletic limitations.
The idea that in any era until recently, you just had to hit a certain bar for technique and never neeeded to also reach a certain level of athleticism/fitness for top level football is just not true. The bar for standard of average player fitness had shifted up another few notches this century, and the game had got faster, but it's extracting that last few percent. Not some huge jump forward where people that were efficient, dedicated nutrition savvy trainers 30-40 years ago wouldn't be able to jump quickly into cutting edge, further refined training regimes and quickly benefit from them if you transplanted them. getting more than fit enough than you'll ever need to play a good work-rate 90 minutes, often twice a week is not something that only became possible with recent advances in dietary/training knowledge. tactics and styles no longer fitting in for older players, so they have to find a new niche or lower(possibly higher too) level is likely to be a far bigger problem.
As an aside, i find it interesting how much more extreme a lot of football fans are on thinking how big the potential individual gaps in fitness are between decades, and how difficult it would be to translate physically from era to era, compared to another heavily skill based, yet athletically demanding sport like Boxing. Every knowledgeable boxing fan knows just as well that dietary/training knowledge is more refined and efficient now than it was during the 15 round era, same as with any other sport. Though they don't tend to delude themselves that every current athlete is an impregnable temple of commitment with no bad habits at all..You get plenty of debate on what era were better overall, or how far back was "too primitive technically" (usually somewhere pre-WW2) but not many that have watched enough footage of all of the post-war decades will argue that the average top ten contender level fighter of past two decades is oviously fitter, in relation to what is practical for the rules of the sport. You would be widely mocked if you suggested that someone like Monzon (despite his smoking and drinking) Hagler or Ali could not cope with the pace of current boxing with it's more refined sports science.
Despite no doubt being on more technically/time efficient training regime than a Sugar Ray Robinson, Duran, Monzon or whatever top ten contender of those era...outputs remain on the same levels and plenty of fighters still gas out in the late rounds (despite it only being 12 ) despite a vastly less intense schedule than 90% of pre-70s fighters. Those older guys were often fighting 5-10 fights a month, between 10-15 rounds each fight at the same pace of current fights. basically, on a purely efficiency for sporting rules basis, being able to get yourself more than fit enough for 15 rounds and multiple fights a month was already well within the grasp of feckin 30s/40s standard of diet/training knowledge. We're talking about a level of physical output much more gruelling than playing two games of football a week, easily doable with enough individual commitment into your late 20s/mid 30s, despite cruder scientific support from personal trainers/data analysts etc..
obviously no two different sports disciplines are fully comparable fitness-wise, and with football being a team sport it was easier to raise the bar up another few small notches for the overall average standard. It was also much less tactically mature/integrated than a more easily defined (in terms of what stuff works and what definitely doesn't) individual sport...but still, fitness is fitness at the end of the day and there's only so much of a certain type you need for any overtly skill based sport where the rules are broadly staying the same; there are ceilings until training for them becomes a mature art for long periods of time. It's very possible that football, at least in the richer leagues, has now hit that ceiling for a long time with its widespread embracing of cutting edge training and dietary support, over the last few decades.
Ex-players that are managers or work in media tend to be more humble and supportive of any advances they see, and they understand that even a small nudge forward can make the difference at elite level. However i've little doubt that for every older player that would really struggle physically (they would likely be no specimen in their own era, or too reliant on an athletic advantage) there would be four or five with a high enough existing level of fitness/athletic capacity to just get on with it after an adaption period - and some gym rat/athletically gifted players that were probably just as fit, or even more so than the average current player, without needing the extra edges of a 2020's perfectly calibrated diet/training regime to get to that level.