Welcome back. It helps to say what times you play in (EU, EST, PST, JP). It also helps to say what your main character name is in case it’s different from what’s on here, so people can look out for you.
Also, what people currently consider endgame may be a little too hard for you to hit/survive if you just hit 99. You’ll want to work on capping merits so you round out your skills and abilities, then on getting capacity points to further boost your character (I guess you at least have 500 if you’re wearing Su3 gear) until you hit master and then can do the grind with exemplar points that other people are struggling with now. Take advantage of the campaigns going on and get as many merits and capacity points as you can in your free time.
I’m not saying you can’t try to join low-level endgame things like vagary and Omen in the meantime, but even those will mostly have other people carrying you through the clears for a while (on the bright side, those events have gone on so long that others have many of the gear drops already and will freely let you have them). If your main is thf, then at least you can provide TH in the few events where that still has an effect. Don’t be discouraged, you’ll slowly build up to better gear and be able to contribute more.
Anyways, my group plays more during late PST hours but there are other groups around at other times. The easiest way into a ls here is having a good attitude and good reputation, or at least someone who can vouch for you from back when you used to play (may not be too many left from 15 years ago!). I’m currently helping 2 friends from the good old days of Seraph catch up with things.