They are a good addition imo though I may be biased since I was lucky that the covenant I wanted to join was the best one for my main spec (by quite a fair gap).. ^^
It would definitely be nicer if these sort of systems separate player-power and cosmetics/lore choices.
Like what if each covenant gave the same covenant ability and conduit traits, but it would be themed differently based on your covenant choice? Sure that means less abilities in the game overall, but what does it matter when most players will always go for the best choice and the other abilities are never used except for the first 2-3 days of leveling on your main.