I keep flip-flopping on this. Currently I don't agree, but really it all comes down to whether a new manager would get more benefit, from a coaching perspective, from training ground time or more games so I've added it as a pro and a con. Other than that:
Pros
- Would allow us to strip down our squad
- Fewer matches would help us out in the league
- More time on the training pitch for new manager
Cons
- Very difficult to attract quality players without any European football at all
- Lose a potential route into the CL the season after
- Less football. There are still some fans left who like watching United play
- Lose the most likely opportunity to use youth
- Less competitive matches for manager to assess players/progress
- Loss of matchday revenue - not insignificant
Kante joined Chelsea from Leicester despite Chelsea being without any kind of European football. EL and ECL are not the thing, quality players look at. Thursday evening to North, East Europe are not really attractive.
To gain the potential route, it would require bigger investment for squad depth which is counter productive. You need bigger squad, but since these competition doesn't pay out well, you would take out from your already reduced transfer budget. Keeping underperforming, unmotivated players around for this competition is risky. They're not happy with just playing EL and domestic cups alone. They're time bombs that would trigger other issue when the team league form is not good. Not all players are selfless reasonable. In truth, sounds like many are selfish, self centered, lacking in situational and self awareness.
It's not that simple to play youth in these 2 competitions. Seasoned pro teams from smaller leagues are well capable of dispatching the inexperienced youth team. With third placed in EL group has another chance in ECL, teams from smaller league are more motivated to play until the very end. And with all the COVID outbreak affecting schedule, you don't want to play the extra round with CL dropout in EL/playing that extra round in ECL after dropping down from EL. So you want to finish first place in the group, which playing youth doesn't guarantee.
38 league games and two domestic cups, especially with a World Cup in the middle of the season this time is more than enough to assess the players. It's not like the whole squad got called up for World Cup. Clubs managers can call up U23 players, and train them if they want too during this time.
All in all, there is no con beside losing another chance to win a trophy, in our situation.