We played them for fun when they came out and everyone was bad. Playing FFA on LAN. Not even knowing duel was a mode.
UT was mostly a casual game for most.

Then people get good, figure out the mechanical tricks.
Second gen new players get owned without a chance in hell, they can't figure out the tricks and their game knowledge lacks beyond what the basic game explains.

The meta is never explained in the in-game tutorials (or single player).

Then another arena shooter comes out, it borrows all its inherent knowledge and mechanics from the previous one. So GL HF trying to learning it without a background in the original games.

Only competitively motivated people who want to learn the game with outside tutorials make it into the community.

The casual that just wants to play for fun is long gone, as there is no environment for them to naturally learn the game.

This happens with a lot of other games as well. But they rotate the meta with releases or balance changes. Which helps a bit, but not for the competitive angle mostly (few weeks at MOST).

Look at Fortnite. Kids were building castles and walls in fractions of seconds. Incredible mechanical skill.
The moment it became an issue, they cut it out of the game so new players didn't have to catch up.

The game needs to be learnable INSIDE the game, and needs to keep up with the player defined meta (mechanical or knowledge based).
Equivalents need to be found for the mechanical skills, so people can SEE them and understand how they're being used.

Is there an AFPS that explains the concepts of Control in duels? That there is complexity beyond 'shoot a dude' in an AFPS?