Light is in no way bad, it's rather just a troublesome element that requires extra work as there is very little resources for strengthening them. Barely any events so no light weapons or eidolons outside of gacha. Also no event eidolons with hp% can make it difficult to do harder content so you'll be forced to scout for players with Hecatonchires (gatcha eidolon) unless you manage to get her yourself.
Though if you plan to use it, we will have a light event in about ~3 weeks. If you don't decide to start now, I don't see you coming close to max break limiting the event eidolon. Which in that case I would skip going light.