PoE2 early access is still months away, so I assume you're talking about PoE1.
In my opinion it's definitely worth playing if you're into that type of game. The monetisation is still very fair in my opinion. It's perfectly playable for free until you reach the endgame, where you'll probably want to spend around 30-40€ on stash tabs. But you've probably played for at least 20 hours before you even get to that point. And it's a one time purchase which costs about as much as Last Epoch. And less than Diablo 4.
Personally I'm not a huge fan of SSF (solo self-found), it does make the game somewhat harder since parts of the game are not designed around this mode. It's supposed to be a limitation. If that's how you want to play and you're a more casual player then Last Epoch might be the better choice, they have a mode that caters specifically to people who want to play like that (Circle of Fortune). But lots of people play SSF so it's not like it's not a viable way to play the game or anything. Playing trade league but only trading for a few things you need (like build defining uniques) is also an option. And in the current league they also introduced an automated currency exchange market which makes trading certain items a lot easier.
I've only played the most recent Cycle in Last Epoch so I can't tell you how the game "now" compares to previous states, but I've enjoyed it. The story is a bit convoluted and there's certainly room for improvement, but I enjoyed the gameplay. Both building your character and the crafting system are way more approachable than in Path of Exile, but still interesting.
Overall I'd probably recommend Last Epoch to a casual player unless you're drawn to PoE's more complicated systems or abundance of content, especially in the endgame.
I don't agree with this at all. Even if you don't want to trade (which only really requires a single premium stash tab anyway) you'll struggle in the endgame if you don't have at least a currency, fragment and map tab. I actually think you need even more tabs in SSF (solo self-found) than in trade league. Because you can't just buy something if you need it you'll probably want to keep way more items. And with the four default tabs you pretty quickly run out of space (in the endgame).
But yes, for the campaign it's not really an issue and I would definitely consider that as perfectly playable for free. And by the time you're done with it you'll probably know whether you want to buy some tabs and keep playing or not.
Tip for people who do want to buy stash tabs: there's a sale every three weeks where all tabs are around 20-25% off.