I use Pale Moon which doesn't have "click to play". Must admit, I've not tried uMatrix, might have to give that a try...
And, I've tried it. Looks interesting, but the main thing that FlashBlock does give is simplicity. A simple Flash icon that turns into a "play" icon when you hover over it. Click, and that Flash element loads and plays.
Doesn't really bother me. One tiny extension and the issue is solved. uMatrix is interesting, but it has the downside of breaking most sites without a lot of fiddling to configure it properly. FlashBlock is a lot less powerful, but does work rather more simply overall.
It's easy enough to allow common frameworks/CDNs across all sites (and then use Decentraleyes to use local copies instead). Anything which breaks after that deserves further attention.