My gaming group has been using Roll20 for 5 years and counting, ever since the pandemic lockdowns began. We dabbled a bit with FantasyGrounds and Foundary during the lockdowns also, but we bounced off of them.
FantasyGrounds was too frustrating to get running on all of our different computer platforms, and getting them all to connect with the different TCP/IP protocols. Some folks in my group used Windows, some used Apple, one guy used Chromebooks, and cross-platform support wasn't really a thing back then. Maybe it's gotten better in the 5 years since?
Foundry was the fastest, but it had a limited library at the time, and required someone to set up a dedicated web server (which nobody in our group wanted to do). It also meant that nobody could work on their character sheets offline between games unless the owner of the host computer kept their computer running and connected at all hours.
Roll20 was the most expensive ($90/year for the Pro subscription), plus the cost of modules and games. There are deals on DriveThruRPG and Humble Bundles, but even so, cost has always been our biggest issue. I won't sugar-coat it: Roll20 is a money pit, with tons of microtransactions. Even so, it's been the best fit for my group. We haven't experienced any of the stability issues that others in this thread have described--but we don't play with Dynamic Lighting or animated maps enabled, we don't use the built-in jukebox, and we don't use the built-in webcam/microphone (we use MS Teams for that). I suspect people who are having bandwidth or stability issues are trying to do All The Things, on a computer that doesn't meet the (hefty) system requirements, and/or with an improperly-configured browser.
We use Roll20 for D&D 5E mostly, and Call of Cthulhu semi-regularly, and also for the occasional game of B/X D&D. And thanks to some Kickstarters and Humble Bundles I've funded over the years, we have used Roll20 for games of Coytote and Crow, Daggerheart, Thirsty Sword Lesbians, and Cypher games like Old Gods of Appalachia RPG and Magnus Archives RPG.