Despite what my ex says, length doesn't matter... or at least it's not the only thing that matters.
The complaint about splitting it into parts wasn't so much about the game being short, it was about a) having a lot of filler and b)having to buy three or more games to experience the complete narrative.
To avoid accusations of bias, I'll use Xenoblade Chronicles as an example instead. There are a ton of sidequests in this game that you have to do if you want to unlock certain things... and a lot of them suck. Halving the number of sidequests would have meant less game, but it would actually make me enjoy it more.
FF7 Remake is just not a complete narrative. By the end of the story the conflict is completely unresolved, and aside from Cloud becoming maybe slightly less stiff, there's not a ton of character growth. Whereas a game like Mass Effect 2 or Uncharted 2 is despite being being part of a larger story. It seems like to get the full narrative experience we're looking at at least 3 games for 180 bucks (if we buy them full price), and potentially upwards of 100 hours. Which... if you really love the game, I guess is a good thing. But in a world where I have limited time, limited funds, and a lot of games, there is something to be said for a more compact experience.
It's hard to judge whether or not the decision was a good one before seeing how the rest of the still undetermined number of parts are done. But again, it's really not about the length. The game's length is perfectly acceptable for an action RPG. That being said, I felt that the original game which took me about 25 hours with doing pretty much all the sidequests besides Chocobo racing (the 3x speed mode is a godsend) provided a more complete and ultimately fulfilling experience than the Remake, which to be clear I liked very much, provided.