That's why I put "(quality)" in my comment, Leverkusen does have quantity but the drop off in quality is too big for many positions which aren't already great to begin with. Don't forget we are talking about CL level teams and it feels like even our discussion kinda shows that the standard has dropped a bit for these teams in the BL.
Another part of this is that there are too few established top quality players and we mostly talk about the talented young guns. That is of course a result of certain long term trends (BL teams having a harder time to keep such players and a focus on developing young talents) and the financial repercussions from Covid.
Leverkusen for example lost A LOT of experience with the retirement of both Benders (pretty much the only players with leadership qualities) and had to sell a player like Bailey to a midtable EPL-club. This is of course nothing new for Leverkusen, they are used to these kinds of buildups but it is a reason why they always struggled a bit and are extremely inconsistent and also notoriously underperform on an international level (I don't expect too much from them in the CL but even their EL results are honestly awful, especially if you compare it to the spanish equivalents).
Don't get me wrong this is not a "lol BL = farmer's league"-comment, I think there are a lot of teams which have good potential and are able to fight for the CL spots but there is a lack of clear top teams while there is an abundance of solid EL level teams around.
Well first of all: what do you mean with "CL level team". It's been three years since Leverkusen last finished fourth and it only happened once in the last 5 years. I'd say the CL level teams in Bundesliga are Bayern, Dortmund and Leipzig and then a bunch of hopefuls (Wolfsburg, Leverkusen, Gladbach, Frankfurt - depending on who is peaking in a particular season) hoping to win fourth place.
I'm not sure covid is even the problem: Leverkusen (€50m gross, €10m net), Wolfsburg (€50m gross/net) and Leipzig (€107m gross, €-5m net) for some reason actually managed to spend some money, Frankfurt had to let go of Silva, but signed their two Scandinavian attackers and Borre (potentially creating a one step backwards, two steps forward scenario) and Gladbach at least kept their squad together (though that will probably cost them dearly in the future). Aside from Leverkusen (whose current crisis (if you want to call it that) looks a bit random actually) it seems quite clear to me that these problems stem from the coaching shuffle during the summer.
I think before that the situation wasn't looking so bad, Bayern were of course (too) dominant and Dortmund arguably wasted a few good years on Favre, but together with Leipzig, who actually made a CL semi and did well in a group of death the year after, the top three were doing okay, with some healthy competition between Gladbach (one good CL season), Frankfurt (one great EL season), Wolfsburg and Leverkusen for fourth place behind them.
I think in general the big problem is EL performance, which is much worse than it has to be quality wise: you either have some team, who is relatively new to European competitions and/or lacks the squad depth or you have Leverkusen, who always go out at the first hurdle.