The biggest issue is management's mentality of "we just need to make the UCL and all of our issues will go away." Every season we don't finish within a UCL qualifying spot, we go out and try to make a big buy or two thinking we're a player away from finally getting to that next level. The cycle of insanity continues, as we fire a coach, sign a useless player, and try again next summer.
We have a core of players who are well past their expiration date in terms of chances we've given them to turn this around. We have too many poor performers on high wages, too many useless transfers out on loan, and too much money committed to buying players in future years on loan obligations. What is the end game? By some miracle, one coach will get us into a UCL spot. Then what? We get embarrassed out of our UCL group when we face elite competition (we'll be a Pot 3 team), and end up back in the Europa League after six games.
We need to stop with the half-assed fixes, we need to stop trying to but a band-aid over a bullet hole, and we need to commit to doing a re-build the proper way. This current roster has no promise, not potential, and a low ceiling. That isn't going to change until we change the players.
We all enjoy laughing at Milan, who surely will miss out on a UCL spot this year to the Roman teams unless they win the Europa league. Their summer was mediocre, but they did what we truthfully need to do; they recognized their core of players from last year wasn't good enough, and they went out and try to make wholesale changes. And sure, they signed a bunch of useless players in the process and very well might go bankrupt because Yonghong Li is as real as Tinker Bell, but the principle of what they decided to do makes sense.