On the contrary, I would say that 0 A.D. has too many features. Building capture being the prime suspect. While some features, like trade and healing, are under-utilized.  This stems from the core gameplay loop being a unit spamfest in the first 8-10 minutes of each match. And it's almost always the same two types of units. Not sure about the difficulty, the current AI is very weak once you get the mechanics right.

That would be an interesting idea. However, it doesn't really make since that the farmer just being near a building should repair it, since he is just standing there. However, what if idle workers (defined that way because their last order was to build, gather, or repair) automagically would start repairing buildings?

The game has very few features, so you don't feel any progression. The lack of progress seems to be linked to having only three phases and very few technologies; the early game is snowballing. The game needs more hardware capping with its progression. Progress is felt exponentially. The brain has more ephemeral dopamine rewards. Playing a game becomes routine due to the scarcity of new things to do or the difficulty of achieving a goal to win.

Looks to be https://gitlab.archlinux.org/archlinux/packaging/packages/0ad/-/issues/3

Definitely need sdl version and kde / plasma version, also are you using multiple monitors? You could try the AppImage at https://releases.wildfiregames.com/rc/ , if it runs would be a strong indicator where to look further into the issue. The AppImage should also be easy to add to Lutris.