I talked about this outside of tftv but A/D could work
The main problem I've heard about A/D from a lot of players is that for red, once a point is taken there's generally little reason to defend it again/retake the area like you might do in CS. Out of any team fps game, CS has the easiest to understand and one of the most well balanced objectives, having an asymmetrical gamemode can eliminate most stalemating as rounds can only last a certain length in which the attacking team has to complete the objective.
I think the best version of an A/D gamemode would be something like mountainlab (although obviously not actually that map lmao) where you have a linear A/D map, but with the change that red can recap the points.
To make this work you'd have to make it so that point captures didn't add cap time (at least not for red recaptures) and make it so the 2nd point caps quicker than the 1st and the 3rd caps quicker than the 2nd like on a 5cp map, giving the attacking team a chance to backcap the defending team, but making it significantly harder for the defending team to backcap the attacking team.
This would basically be like 5cp cut in half and made into A/D, it might eliminate stalemate issues as the attacking team are always under pressure to cap last, but the defending team always have an incentive to push out on an advantage to retake an if they get enough picks on last. The issue with this type of map is that it eliminates midfights compared to 5cp (which are a pretty interesting part of the game) and it's always going to be significantly harder to balance an asymmetrical map compared to a symmetrical one.
Lain's A/D koth gamemode also sounds pretty interesting and I'd like to try it out.