Crowded? The last game had three main playable characters
That's already two too many. The more characters you play as the less the lead actually gets. There is not need for 3 or 5 or so on playable characters. 1 Should've been enough, 2 is pushing it, 3 is a crowd.
and four supporting NPCs (five if you count Kyrie who wasn't even on screen).
Of which we could've gotten rid of most and nobody would've been the wiser. Remove Trish and Lady and the story wouldn't be any different and Morrison hardly contributed to squad. Nico is the only one that has any excuse to be there so she can make arms but the rest of the didn't do anything that was so critical that they
had to be there. Make the Artemis and Cavalier plain bosses and what's left for them?
The Devil May Cry cast is nowhere near as large as the ones from franchises like Resident Evil or Metal Gear even if you leave out characters that only appeared for one game.
DMC5 is nowhere nearly as large as RE6 was, nor any MG game, to accommodate any large cast and any other RE game at least had the cast contribute in some way, be it to just bite the bullet. These forced cameos offer nothing beyond fan service and they cheapen the characters. Both Trish and Lady were these iconic figures in their respective games and made legitimate impact on the story but there is nothing left of those traits, they have all but nothing to do here and they deserved better than a glorified cameo.
Characters getting along is not inherently boring.
Inherently and intrinsically, no, but this is them getting along and it's nothing. At lease with a bit of friction it adds adrenaline to the situation and it is a definite step up from them just being there, which is what we have now. There is nothing wrong with a rivalry, either. Some characters have become iconic because of their rivalry.
And really what reason is there for them to have a rivalry?
Pick one. Anything would be fine. Work, a fight for the office, a trinket, a philosophical difference of opinion.
Characters getting along is not boring.
Welp, here it's not doing them any favors and it's boring.