Mass Effect 3 feels like a frustrated writer spitting on the previous games in the series because he had to work on a sequel to someone else's work.

Mass Effect 2 is a darker game than Mass Effect 1, but both games are "Space Opera" adventures. Mass Effect 3 is not a Space Opera, it is a war story begrudgingly told in space. It's not impossible to do a genre pivot like that well, but Mass Effect 3 doesn't do that well. Mass Effect 3 feels like the (new for this game) writer's gritty unrelated war story wearing the skin of the Mass Effect series grotesquely stretched over it's face because it's not the project the writer actually wanted to be working on. Plot hooks and intrigue as to the true motives behind the Reapers and overarching narratives from past games are completely thrown out for derivative and uninspired motivations delivered by ridiculous deus ex machinas that weaken the past games and their stories by association and retrospective context. While there are some nice character moments with companions from the previous games if you import a save file, the game at time feels outright contemptuous of being part of an ongoing story and like any "happy outcomes" made possible or easier through past decisions are handed over with a scowl like the writer's hand is being forced. Shepard no longer feels like your character and simply the writer's pre-written protagonist, any pro or anti Alliance, Council or Cerberus sentiments you pushed in past games thrown of the window for the pre-assigned ideals and beliefs of the new writer's ideal player character.

The gameplay can't even save Mass Effect 3 if you enjoy playing the series on a higher difficulty. Sure, the gunplay and usable powers are some of the most fun they've been in the series, but the enemy and encounter design comparative to previous games is a tedious, unfun slog of drawn out encounters that take the weakest points of Mass Effect 2, the various arenas of wave survival into bullet-sponge bosses like on Horizon, and seem to base every other combat encounter on the same template.

The only things that come close to saving Mass Effect 3 are two truly incredible DLC in the forms of the Omega and Citadel DLCs, which are easily two of the highest points in the series, but even if you save them for last to end on a high note you're still going to have your spirits dampened by the infamously terrible ending that throws away three entire games worth of decision making for a choice between three pre-canned endings.

The multiplayer used to be fun for a laugh with friends, if not particularly deep or fleshed out, but it's been over a decade since the original version of ME3 released and LE3 removed the feature entirely so it's difficult to enjoy now.

Mass Effect 3 is overall an insult to the two games that came before it, only worth trudging through if you're commited to seeing your Shepard's story through to the end.

Even if it doesn't wrap up the trilogy in a very satisfying way I think this is a great game.
My major gripes with it are that the game feels incomplete and short without Citadel and Omega DLCs and that the dialogue and choices have been somewhat simplified. The latter especially feels like Shepard is a more flat character that for some reason just cares about saving earth no matter what past you chose for them in past games.
Still has some amazing characters, locations and missions which save it from being a failure in my eyes.

I'm not going to go in depth here, but essentially, Mass Effect 3 is a mostly disapointing finale to the trilogy. The game lacks RPG mechanics and dialogue choices. On a whole, it feels more linear and driven by combat, rather than primarily focussed on interesting storytelling or character building like the previous two entries in the series. Your decisions in this game (and decisions from elsewhere in the trilogy) feel inconsequential here, and the ending is thoroughly unsatisfying. After all these years, I'm still bitter about it.