Changing coaches at the start of the season after a few matches have been played sometimes happens often. but the results are sometimes always not good enough for most teams. But if the current coach is really monotonous and continues to make the team get bad results then I think keeping him will also make the season a waste. So it would be better to take the risk by looking for a replacement that is considered to be better. But Erik Ten Hag must also be given enough time this season to show his hard work in building this squad. And who knows, this club will bounce back like what happened in the first season when Ten Hag came to this club.
For Manchester United it's very much needed even without considering the short term service back they will suffer resulting from changing of coach, most persons would want to think that basically he should be allowed till the end of the season so they Manchester United can start off on a new bar and season where they are going to have new coach train with the player and make his selections and adjustments before the new season kicks of but in the case of Manchester United, they have literal has ro go through a whole lot in recent times and idt not getting any better, this coach in question, has been given more time, this is his third or fourth season at Manchester United.
Regardless, I still do not think it's ideal or a good idea to change him while in the middle of an active season, it the management of Manchester united knew things could become this bad for the club, maybe they would have changed the coach when last season ended, that would have enabled to new coach to train with the team and get to know the abilities of this players even before this current season begins.
Right now, I personally fell they are stuck, even if it be possible to change a coach in the middle of an ongoing season, I still do not think it's a good idea, doing that may or can likely put the club in a more serious problems than they are already into, specially if the new coach won't be a very well experienced one who is really good at the job.