It all depends on what you expect to get out of the game. There hasn't been an expansion in a very long time--there isn't likely to be any more expansions. But the game is not as "dead" as naysayers would have you believe--there are, indeed, people still playing it, and enjoying it; if there weren't, they wouldn't bother with keeping the servers up. Is population low? Compared to FF, WOW, ESO and the like, definitely. Is there no reason to bother? Not at all, depending on why you chose to play.
Even though the addition of new content has ground to a halt, and there is unlikely to be anymore, there is still a ton of content--a ton. Literally hundreds of hours of gameplay for free, hundred of hours of unique content, not the same content on a treadmill.
People are going to bring up the flaws--those flaws exist. No new content, no new raids, which is the source of most of the complaints. Also, class balancing at endgame is whack, that's true. Both of those complaints are at endgame; until the point you get to endgame, however, the game is fine.
Because of the age of the game, most of the playerbase is sitting at max level. They don't run low level content, so unless you join a guild that likes to run low level content, you will wait in a queue forever for a low level dungeon or PvP; it's effectively non-existent. Open world events go a long way to filling that void, however--many players, myself included, spend their playing time shard hopping, going from server to server whenever a zone event pops up. It's spontaneous and varied enough to be fun; it's rare to not find people participating (I should point out that that's the case for 3 of the 4 world maps; it's been my experience that people just don't participate in events on the Brevane/Duskin map, for whatever reason). Is it the same as dungeons? No, I'm not claiming it is. But it is group content, and it is still fun; that's not just my opinion, it's the opinion of others that participate.
If you're an "endgame is all that matters" player, then don't play. If you're a player that likes questing and exploring, then give it a shot--it doesn't cost you anything (oh, and don't bother spending any real money, for Prime or anything else, really, unless you just really want to; you'll get the gear that you need for open world content easily enough through questing). Questing, for the most part, isn't too bad and there's a ton of it. The quests are laid out pretty well, with most of the questing being story driven quests that encourage map exploration, with a minimal amount of boring fetch/escort quests (except for Planetouched Wilds, that zone can get bent). Mechanics are what you would expect from a game a decade old--this isn't action combat, it's old school tab-targeting/global cooldown; if that's not your thing, don't bother with the game. Graphics are still pretty good, for a game a decade old. If you don't enjoy games that don't threaten to melt your brand new video card, then don't play, it's not for you. There are some bugs, bugs that haven't been fixed for years, but I personally haven't come across many "game breaking" bugs; that's just my experience.
The short answer is, how do you play? Are you an intensive, late game, raid centric player? This game isn't for you. Are you a "I want a game to pass the time, that has a lot of content, and I can play for the low low cost of free" player? Then give it a go--you haven't lost anything.
