Welcome back Veiq. My opinion below.
Too much has changed. PK system is different, no penalty for being red. When a player kills a red toon, nothing is dropped. If a mob kills you while red you have a chance to drop something into jail, but you can buy it back out. There is no Grade penalty. My advice, look for S Grade everything you can, then put that gear on your L1 toon, follow the newbie guide to get to Level 20 in about 15 minutes. Pick you main, and at least 4 boxes, more likely 5 boxes. Level them up together in duo's. Melee main toons, need a WC, BD, PP, SWS and Cat buffs. Mage mains need an OL, BD, PP, SWS, Pony, SE for Wild Magic and Empower. Mage's exp faster than melee. This is pretty much a solo game. You can find clans, some are there with active players, but most player are already 80 plus so expect little help until you get up higher level. On TI Private Warehouse is stil active and helping new players I think.
Yes you will have to invest in the game to be competitive. But maybe you don't want to be. If you are a mage, your goal is Antharas Lair, if you are Melee you will end up in TOI. How much to invest is up to you. I know of people that have/had over $100,000 in their toons. I know others that don't spend $20 per month. They aren't even on the same field when it comes to damage or capability.
One of the biggest problems I see with the game is that the pay to win events have such low odds of success, only the biggest whales can afford top items. So people spending less feel defeated early because they can never keep up or even dent the whale bully's when they get bored and start wreaking havoc. Thankfully most of them seem to have left the server because they ran so many other people off, not many left for them to hassle.
Should you play? If you have time, nostalgia and don't mind playing solo for a while go for it. My advice don't pick a box/healer as your main, nobody needs them as most of us have our own already.