My keyboard privacy is one of the most important things for me since it includes literally everything I type. Signal messages, 2FA, passwords, web searches, etc. That's a pretty big gamble to just assume Gboard isn't spying (even with network permission disabled), especially on a profile with play services.
I don't personally have that much of a problem with FUTO Keyboard. Do the people complaining about it not change any of the default settings? Under text prediction, advanced parameters, I set Transformer LM Strength all the way to the right to always use the Transformer LM. Also, under Keyboard & Typing, I changed Automatic Spaces Mode to legacy since I was getting weird results with the default. My experience is good enough that I don't even think about my keyboard anymore.
FUTO Voice also doesn't have problems though I don't use it that often since I think clearer when typing than speaking. I installed both since I can remove microphone permission from the keyboard that way.
As someone who was originally on a Blackberry and then on the earlier iPhones, I never got into swipe typing so that's not a feature I even use. I also can't speak for non-English keyboard users.
The biggest frustration with FUTO keyboard for me is that their popup on keypress is so obnoxiously bad that I have to keep it turned off. I don't know why they didn't just mimic Gboard's style for that like they did with other parts of the keyboard. But I've learned to get by without it. I mostly just look at the word suggestions as I type anyway.