Believe it or not, I can assume that Ten Hag is not a coach who can restore Manchester United to the glory that Ferguson created in the past. Ten Hag doesn't have that much capacity and ability and that's also because the squad depth is never as good as it used to be. Eras have changed and Manchester United's dominance in the Premier League has been completed since Fergi retired.
It cannot be denied that Manchester City is a team that will continue its dominance because of its financial strength and the ability of its coach. Liverpool, Arsenal and Chelsea will certainly struggle to stop this dominance, but Manchester United doesn't seem to have the ability to do so. Manchester City may fail to defend their title, but we have got proof that they can dominate so far.
Well he might not be as good as Sir Alex Ferguson, but he really tried upon his arrival to the club and helped them to get into the Champions League by finishing 3rd place in the standings, like you said the squad depth is not as good as it used to be, due to several reason especially the injury crisis they experienced at the early stages of the season up till this moment, i believe if they could work on their squad depth and give the manager the rightful players he need, then their could be an improvement.
To be honest, Manchester City were really blessed to have Pep Guardiola as their manager as well as wealthy owners that are ever ready to back him up financially to help him succeed, however i think their dominance would come to an end very soon cause other teams are ready trying to strengthen their team and meet up the standards of City.