Path of Exile has been around for quite some time now. The passage of time can be quite tricky and you'd think that something just happened only yesterday, like the official release of this game or the good old beta days. However, it's true that Path of Exile is no longer the new kid on the block, but that's only a good thing since it's now an established title in the action role-playing game genre.
One of the side-effects of a fairly popular online game that has been around for a good number of years is there are players who've dropped it after some time. They may either be those who stop playing for a little while until the next major content update comes around with new enhancements and new PoE items, those who merely play intermittently, or those who've just quit the game outright. Let's focus more on the first category, which is actually a whole lot of Path of Exile players.
If you happen to be a player who left the game for a good while and recently decided to come back, expect a few challenges along the way to getting used to it again. For instance, while the game still controls the same way, the progression may be a bit different due to patches and content updates added since the last time you played. These changes can be drastic enough for you to require a change in the way you think about the game in general. Your existing game knowledge may be obsolete, so you may want to brush up on what's new.
This is definitely where the community comes in as you can ask questions and refer to guides and notes on what's different and what remains the same. It shouldn't be impossible to get back on the saddle since the basic mechanics of the gameplay will always be the same. It's not like playing action role-playing games is rocket science, after all.
But with that, you then have to determine if you still want to pick up where you left off and play one of your existing characters or start a whole new one. Either way is fine, but perhaps you'd get a better feel for the changes by playing an old character and see what plays differently and what stayed the same. At the very least, you get to see if that character build still works as well as it used to or if something may have changed that.
It's also a good way to get to the newer features and areas. If you start with a whole new character, you'll have to grind and level up before you get to see a lot of the new stuff that you missed out on. But with a character that has been leveled before, you can get there faster and see what's new for yourself without having to go through the busywork beforehand.
You may also want to see what new Path of Exile items, builds, skills, and so on may have been added. It's recommended that you look around in standard league first before you jump back into hardcore league or participate in a race or challenge league. Getting your bearings back is pretty much the most important thing when you're a returning player in Path of Exile.