Branching is good on and off paper and the game would be objectively better if it had better branching (incentive to play non harem paths).
I don't know...I realize more and more that I don't try to get all the paths in branching games anymore. Some of the most extreme examples would be BaDIK or ORS and for the former I still haven't played all the branches of the last update and for the latter I settled with one path and didn't do any other.
Maybe if the game is done and you really want to enjoy it to the last with a considerable time investment. But branching also means the player has to go through a lot of the same content multiple times, which either lets it grow old very fast or leads to skipping large parts of the game, which hampers the immersion in my opinion.
Add to that some unskipple BS like the some of the mini-games in BaDIK and it gets really annoying.
So the way Cari does it with Eternum by focusing in one main "canon" branch has some downsides, but I wouldn't fully agree that branching out makes very game better at least not with tons of caveats around it.
On the other hand I have to admit that the choices in Eternum are arguably the weakest part of the game, because a lot of them are either insignificant or the right one is very obvious which also makes them kinda pointless.