It's a difficult balance, indeed.
You definitely need them to be/remain competitive (in the short term) but not in the long term, of course.
In my division/country, they make a difference but if I promote to D2, I'll be cannon fodder next year (the gap to teams there is huge), so I'm already counting on getting back down, even if I do get up this year
But I do think it would be good, to make such players more "available" to lower league teams.
Also, who knows? Maybe one day the game will allow for veterans to (somehow) be mentors to rookies, that would be neat too (and realistic even)