I often cite smaller games because people are unaware of them or vastly underinformed. So if you like Darkfall’s prowess system, you can go play that right now in Asheron’s Call 1. Seriously, that system existed in 1999, although games did not have achievements at the time. You could even be playing the PvP version on Darktide!
To explain from the comments on that post, AC1 never had level adjustments. Levels are (were) estimates of relative power, not like in most MMOs where you must fight within the range of a few levels or there will be massive penalties that mean instant death. Level 30 archers can (could) hunt level 100+ monsters just fine with the right preparation. Levels give you more skill options, but the rest of the xp/skill system work(ed) exactly as described: doing things gets you a pool of xp that you can spend on whichever skills and attributes you like.
AC1 did mix in a bit of use-based skills by giving extra “practice point” xp for skill use. This involved an interesting formula that rewarded you for doing increasingly difficult things (rather than repetition), but it may not even still be in the game, so I am not going to spout algebra just now.