People who care about numbers will use those guides even if there was infinite covenant swapping available.
Blizzard definitely messed up on making it impossible to test covenant abilities after the selection is made. But criticizing the concept of a meaningful choice is missing the mark I think. If I encounter a puddle and have the choice to step to the left or right of it, that is an utterly inconsequential decision. But if there is a coiled rattlesnake sitting on a pile of cash on the left, and the right side is clear, THAT is a meaningful choice because there are actual ramifications for the decision. Some people will take the risk to get the reward, some won’t find it worth the risk.
There is nothing wrong with consequences for a decision. But as rarely as Blizzard actually balances their game, it becomes more problematic.