So we are in the same boat there.
This is my suspicion, yes.
I would personally only use a Raspberry Pi 4 for a 1-user Nextcloud install (as they are very reasonably cheap, and a good value for what you get), and yes, I would put NC 17 on it at this time. And this is with the Nextcloud data dir and DB moved out to some decently fast USB3-attached storage.
A Raspberry Pi 3 is just a little too slow for comfort, even for 1 user (and I’ve tried it), I say. I would personally use a Raspberry Pi 3 for, say, a Pi-Hole.