Have you played the game at all lately? We are not talking about 0.5% dps gain or something like that. Having the best corruptions in the game vs. having the worst is more like 40-50% dps difference. I know not everything is about competition in WoW but you brought it up. Lets compare two similar geared characters only one of them uses the best available Azerite traits and the other one uses a combination of the worst ones. You will see DPS difference of at least 20-30% not 0.5%.
Implying that the difference between covenants will be ~0.5-1% would mean that the abilities have either very low impact on the game (would be OK with me) or be almost perfectly balanced (would be OK with me). But looking at their latest power systems Azerite and Corruptions, how likely will Covenants be either of those two things? Exactly.
The only way to save this system is allowing players to switch covenants in an easy way.