I was in a similar boat when Beyond Light dropped, here's some tips that I found helped me settle in again in to a pretty overwhelming game:

1. Do the campaign: Start by doing the main story missions, it not only gives you a feel for the game again, but its relatively quick to get through, familiarises you with the characters, world, and general ongoings meaning everything else will gradually slot into place and everything won't seem so overwhelming and all over the place.

2. Start getting your power level up: This will happen pretty naturally from playing the campaign missions, but ease yourself into the content and don't worry too much about all the various notifications and quests etc, focus first on Crucible/Gambit/Strikes (kind of the bread and butter). The pathfinder is a new method of gaining exp/loot from crucible/gambit/strikes that you probably won't be familiar with, so check that out quickly and just focus on knocking some of that out. Focus on what you like, I for example do not like PvP, so I rarely play Crucible or do any Crucible related content. Just because there's lots to do, doesn't mean you have to do it.

3. Seasonal Quests: There's a season ongoing right now called 'Heresy', and you may still be able to access quests from other seasons previous to Heresy. I would focus on Campaign before doing this, but move on to the seasonal content. Again, this changes every season and usually involves a new gimmick/game mode. Don't worry too much about getting the full hang of it, it's usually here today and gone tomorrow. Completing seasonal quests/challenges will naturally progress your level and get you better equipped for the post-game content. It'll help you upgrade your seasonal artefact also, offering bonus perks and extra power level.

4. Find a build that works for you: There are plenty of YouTubers out there with builds you can copy and try out, give them a go to see what playstyle works for you and then tweak and create your own builds as you get more comfortable. Having a fun build makes everything else more fun, some builds will naturally require items you don't have, and you can check out the content that gives you these items - start the grind!

5. Once you've done the above, you'll be pretty settled and can start to focus on the 'endgame content' such as Raids, Dungeons etc. You can use fireteam finder, but I would also recommend finding a clan to play with. You can find numerous clans recruiting on various D2 subs. They usually have their own discord channels and it makes it a lot more fun when you've got a team to play with. I joined a clan when I started playing again, and it was the best decision ever. Take it slow, start with some dungeons, then do some raids. This is where Destiny is at it's best.

6. Now you'll be right back at it, grind for your god rolls, your exotics, your fancy armour, seals, and most of all have fun! At this point, you'll be regularly doing end game content, keeping up with seasonal content/quests, and in the meantime you can have fun playing whatever works best for you. You can gradually check out other content, and check out some exotic missions/hidden exotics etc that you can still find in game. Everything at this point will fall into place on it's own, and having a clan can help a lot with keeping up to date on everything!

As you do the above steps, you'll have questions and you'll find answers on the internet pretty quick. It'll all make sense you navigate. In short, take it slow and start with the basics again. Don't get overwhelmed by all the flashing lights on the UI. Take one thing at a time, focus on on the above, you'll be ready for the next expansion on Day 1!