One does, every so often, get the sensation of going in circles since SAF stepped out of the chair. The club has a strong history and a powerful international standing. The latter possibly diminishing, as football moves on and new history is created.
The seasons move on and the club lacks stability on and off the field. This makes United's star diminish and deters many possible signings. Gakpo, Nunez, Kante, de Jong, to mention a few. Not saying that these would be excellent signings for United, but they prove a point. de Jong stands out as he flatly refused to leave Barcelona even after they wanted to ship him off and United had a great offer on the table.
During time of success and stability, players would probably be less likely to snub United so easily. Especially for another EPL club. These players also play in positions where getting regular playing time looked very likely. Yes, I know that SAF also had big players turn him down, but they often had other reasons than better prospects in a better/different PL club.
Changing managers every 2 years does not seem to be working in the long run. The different managers have different playing styles. Changing style and refitting players is not an easy task. I believe that the club can't find long term success by changing managers and hoping they can make it work. The club itself needs to have a philosophy on how United should play. Then find a manager who can make that work. Maybe that starts with Ten Hag, maybe not. Most changes in style require everyone to adapt, and that means rewiring because so much is muscle memory and on-field relations. If the whole team needs to adapt every 2 seasons, that explains the variations in performances. It also explains why player A can't "play a simple pass" or player B "can't run". Player A might just have to spend too much (every second counts) figuring out where to pass. Player B might just be unsure if this is his man, and have to get an overview.
ETH will naturally be looking for good players to fit their intended position and his style. Whenever a change in management comes along, this player might not longer be a good fit. It does then not matter if the player is world class, as small changes in structure might mean changes in responsibility and what abilities are needed.
That being said, the current sensation is a grim one. With off-pitch incidents making bigger headlines than the performances and results themselves. Perhaps this is okay, for now, seeing as even the senior members are very error-prone and the whole team seems to switch off and be at low morale.