I was chief moderator on the original CZ Forum for 4-5 years, with some administrator rights. During that time, we ended up changing vendors and software several times. It was only after a couple of the members ponied up and pulled together some money, and ongoing support from the membership (through fund-raising on the forum) that we were able to get a system that was stable and powerful. I spent a lot of my time trying to work with the vendor sto get problems straightened out and access set up for new members.
Unless you've got really good tech people working as administrators, it's a lot tougher and more expensive to maintain one of these systems than you'll ever know. And it's NOT free. As membership climbs, so will the number of problem incidents.
The CSF never had as many problems as we did on the CSF -- which is why I never said much. I KNOW some of what they were dealing with.