I suppose it depends how you look at it, but this mostly doesn't bother me. Success is all relative and I pay more attention to my team than I do others. For example, I'm proud of the fact that I was able to take over a struggling BHL team who had been in Bronze for 5 years (had to win a playoff series to avoid being demoted that first year) and was able to promote to Silver after 3 seasons. To me that's more satisfying than taking over an already good team. Now my first season in SHL, there are 7-8 teams that are far superior to me... and the rest are equivalent (give or take a rating here and there). My goal is to stay in SHL and see where I'm at in 2-3 seasons. I love following each team, but don't really care who promotes/who doesn't this year. Every team starts from a different place.
Also, you want COM teams to be somewhat strong - or start off strong - as I would assume they don't improve much over the season. And just to be competitive in general.
Where I do agree with you is that when a manager promotes or racks up wins, their reputation gets jacked up and it increases the chances of free agents signing with them over another team. So a manager who takes over an already stacked team will get the benefit in signing players - which I've stated in another post that I don't agree with. At least not to the extent that it happens. For example, a free agent recently rejected my offer and signed with another team (same league) who offered him $200K less. Ouch. But that's a discussion for another thread.
But we can only hope that those managers who take over good teams are like Peter Chiarelli and totally ruin it