Hello and welcome back. Yeah after 9 years of development and content, it can be overwhelming for sure. What I would do in your position, is that I would start completely new character. They added tutorial achievement into game and they have made new player experience much better what is was at very start. So new character and start leveling it up and every 10 levels you will be offered main story quest, do those and explore the maps. GmaFog runs on Saturdays map clears on low level zones so just jump on in those events and of course don't hesitate to ask help from the guild. I'm fairly sure that there are others who are in process of leveling up characters and if not, I'm 100% sure that there are people who needs map completions so they can help with their higher level characters as they are always scaled to zone level.
Not sure if you own Living World Seasons or expansions, but after getting lvl 80 and main story completion, you want to proceed Living World Season 2 as it is prelude for first expansion, Heart of Thorns. After Heart of Thorns story, next will be Living World Season 3. That is prelude for second expansion, Path of Fire and after that will be Living World Season 4 and Icebrood Saga. Those will lead us towards 3rd expansion, End of Dragons and that will be released around February 2022.
Also after getting to lvl 80, you start earning Mastery experience and once you get Mastery points though achievements and exploration, you get to open extra skills. Heart of Thorns brings gliding etc. lovely things and Path of Fire brings mounts as masteries.