It depends on the profession/build how much you can benefit from Celestial Gear. Obviously Hybrid builds benefit the most. In Open World and Story Misssion builds suited for celestial gear provide a lot quality of life. Another area where celestial gear/builds shins is WvW (roaming).

And even in so-called endgame content, e. g. Raids, (CM) Strike Missions and (CM) Tier 4 Fractals, I would suggest to find other people to play with, if your group complains about you running a celestial build. Assuming of course that your build is suited for celestial gear and you know what your are doing.