One of the things I love(d) about GW2 is that they promised at the start that they wouldn't invalidate your gear, and they've stuck to that pretty well. This is a direct violation of that, and sets a very bad precedent..
This feels like a huge f-you to to folks (like myself) who worked hard for a set of legendary runes so we could easily change builds and gear up extra toons without having to ever farm/buy runes again. Now, we have to farm relics just to recreate our existing builds. It's a straight up QoL regression.
It's also taking functionality away from players without lege runes, as they will have to farm relics just to bring their existing gear up to the level is was at before, but this is a one-time thing, and IMO it's somewhat compensated by the minor QoL improvement that relics give people without lege rune sets.
I don't dislike the relics system itself, I just think they haven't fully thought through the impact on existing players and the precedent it sets. Making the relic slot function as a lege if you have 6 lege runes seems like it would largely fix the problem.