As Cephrir pointed out the final 3 vote encourages people to not play well or more under the radar. It's just the strongest player remaining getting voted out, usually making for a more lackluster FTC. Very rarely do previous alliances play a part in the F3 vote.
There's the argument that with a F3 FTC, the obvious threat vote gets pushed back to F4 which is kind of true, but there remains much more room to maneuver. And it's usually much more unlikely for a goat situation to pop up where there is one obvious winner. It also makes FTC much more interesting if you're arguing against two opponents and taking into account vote splits and such imo.
Basically, FTC are usually more interesting with a final 3, and it doesn't sacrifice anything super interesting gameplay wise.
The current actual survivor twist where there's now no vote at F4 is getting a little much, and it wasn't necessary to remove the F4 vote. The whole nitty gritty endgame is now essentially squashed - even ignoring the fact that the F5 is essentially "whoever doesn't have an idol is going home".
Spoiler: slight winner spoilers
I always thought the firemaking challenge should be done at F3 instead of F4. That way you still get the adrenaline of seeing the cast dwindle to two, but it's probably the more passionate players that make it through.