If you’re asking seriously... tmux has a unique interface which is probably not worth learning merely for the purpose of managing multiple active sessions. You also can’t wire it to accept proper GUI commands with the mac command key. Tabs make sense.
I'm not saying you have to have tabs, if you want to paint your terminal pink with yellow fonts and render it upside down then go for it, but I'd like tabs :)
If you have 2 tmux servers with different hotkeys you can totally nest them safely. I have a different hotkey prefix for my machine and then leave the default for servers. Works great!
Alacritty isn't actually super fast, the author just opened three other emulators and decided to call Alacritty "the fastest terminal emulator on earth".
Kitty is much more full-featured and super fast. I've switched to it and love it to bits.
EDIT: Ah, it's not available for Windows, too bad. It's the best.
The lack of tabs is a feature for some of us. After all, why have tabs when you can have tmux? :)