AI games give very little exp.
1v1 games against humans, especially humans with higher skill rank than you, gives a lot more exp than 24+ player lobbies, and have shorter match times. If you really want to grind exp, jump into matchmaking or coerce people into 1v1 lobbies.
For example,
B1688554 28 on Desert Rumble 1.02 got you 55 exp for over an hour of game play. If you were to get crushed in a 4 min 1v1 against godde, you would get maybe 275 exp? The system ain't fair but exp only changes your 16x16 png image. But in a sense, are you really learning good gameplay in large team settings? Its common consensus that multiplayer ranking systems make people think they're stuck in "elo hell" because of teammates because in team games players generally need to rely on the performance of teammates. The Elo system itself was based off of chess, where the outcome is all that matters, and the outcome is entirely determined by the skill of the two players. And that system is generally the base of every multiplayer rank system. Which would make 1v1 the purest, easiest, and most accurate to the spirit of the ranking system.
Additonally, level is like overdrive, it has diminishing returns. To double your level, you need to quadruple your exp. This is like playing cookie clicker but all you do is click the cookie instead of buying the cookie-generating things. Progress slows down, and then becomes near impossible, just a function of time for no tangible gain.