The huge switch from SMS to WhatsApp in Europe was well done before they were acquired by Facebook. By then the damage was already done, because the network effects made it very hard to move away. By now, many people I know also have a Signal account, but it doesn't really get off the ground as long as, say, 30% of every group chat does not use Signal.
Year, back prior to the Zuckification I'd say it was a very clear upgrade for everyone in essentially every way. Dirt cheap (much less than even minimal texting), installable everywhere, adopted solid E2EE far ahead of basically every major player (2016!), it was great. USA had everything worse for a long time, and many things still are.
But once it landed in Zuck's hands, I no longer trust it one bit. Abandon ship.