If you're expecting a "mobile first" or similar GUI where most of the screen is dedicated to whitespace, basic features involves 7 or more mouse clicks and for some reason it all gets changed every ~6 months then yes the 7zip GUI is terrible.
Desktop software usability peaked sometime in the late 90s, early 2000s. There's a reason why 7zip still looks like ~2004
You could have taken the 10 seconds to type in "PeaZip GUI" and seen that it is not a mobile interface and it is indeed much nicer than the 7-Zip interface.
Instead you chose to make a useless snarky comment. Be better.
PeaZip is popular? It seems a lot less tested than 7zip; Last time I tried to use it, it failed to unpack an archive because the password had a quote character or something like that. Never had such crazy issues in 7zip myself.
Hence why PeaZip is so popular, and J-Zip used to be before it was stuffed with adware.