Believe it or not, I enjoyed the game actually. You'd still be retarded to not recognise that it's the Source engine doing all the heavy lifting for the game and not the actual game content.
Actual gameplay, especially in comparison to HL1, is shit. Half the guns in the game pack no punch and are unsatisfying to use. All the fun sci-fi weapons are gone, with the old arsenal getting nerfed into the ground due to muh realism and muh gravity gun. There are now cancerous infinite ammo crates scattered throughout the game which I'm not even sure how to comment on since it's such a lazy, brainrotted thing to add into an FPS. After you get the RPG (which you'll never find ammo for outside of boss battles btw), all the boss fights in the game will turn into a repetitive quest to reach the infinite rocket ammo crate while under heavy machine gun fire. You will find yourself constantly low on ammo for the few guns that are actually fun to use, always having to either switch to unsatisfying weapons or improvise with the gravgun because their le smart supply crate system which they've jerked themselves off about so much in their dev commentary never actually gives you ammo for the guns you use most often. Additionally, you now have stamina, with both sprint AND flashlight depending on it, which makes combat much less energetic and completely ruins pacing in dark areas. Enemy variety is just as miserable as the weapon variety - it's just good humans, bad humans with heavy vehicles and some miscellaneous technology here and there like mines and turrets, zombies and antlions sometimes. Xenians and all their unique animal behaviours? All starved to death or something, sorry not sorry and here's an occasional non-combatant vort NPC for your trouble.
Story is just as mediocre as well. ALL of the characters are complete retcons, some completely nonsensical (Judith) and others just random (Alyx). You've met neither of these people before. Barney is canonically that guard you get to see for whole 5 seconds at the very beginning of HL1, but realistically he's just every guard you've ever met (and possibly killed) during the course of that game. Same with Kleiner, who's just all of the glasses scientists at once. Eli is even worse since while he's canonically the guy that lets you out of test chamber rooms right after the resonance cascade, again, he's just every single black scientist you meet during HL1 except he doesn't even look like the original model at all. Other characters literally didn't exist in any way or capacity, yet act like they've known you for years ev&oe you've JUST met. Everyone is constantly either talking like you aren't around at all or making bizzare pauses, as if Freeman the silent self-insert was actually having a real back-and-forth with them. Unskippable story segments in general are very long and hurt the overall replayability of the game a lot since you stop giving a fuck about their dialogue after a second/third playthrough already. Every single rebel bum in the game somehow knows who you are and what you did in HL1 even though not a singe retconned character was around long enough to know or bear witness to it (Kleiner and Eli have most likely already evacuated Black Mesa by that point because Barney already canonically does in Blue Shift). Furthermore, the game makes it look like every member of Black Mesa staff not only survived all the events preceeding HL2 by some miracle but was also able to regroup around the general area of City 17 despite supposedly being constantly relocated around the globe by Combine, which is just wow isn't that so amazingly convenient! In HL1, your end goal was to escape enter another dimension in order to kill the head of a contained, on-going alien invasion; in HL2, your end goal becomes toppling the regime of an alien inter-galactic empire that completely enslaved the entire human race in 7 hours and kept a strong occupational government for the next consecutive decades - an absurdly unbelievable and suicidally optimistic plot that somehow works because both you and Alyx have impenetrable plot armor. Oh, and Valve themselves also have no idea who Gman is and what he wants which really shows by how they keep retconning both him as a character (HL1 -> HL2) and his intentions (HL2Ep2 -> HLA) - they will never reveal who he is or what he wants even partially because why bother writing actual endings to your mediocre stories when you can just end them on cliffhangers every single time LOOOOOOOOOOL.
Episodes can't really be called DLCs because they're nothing but just more HL2 content. They add no new weapons and only several new enemies, their plot is just a direct continuation of where HL2 ended and like I said it's just more HL2 gameplay because Valve cut way too much content from HL2 over the course of its development and wanted to actually finish at least some of those old ideas (antlion caves, for example).
Anyway I've wasted enough time typing all of this shit out. tl;dr: the game has very little to show for it other than its physics engine shenanigans and also good mapping I guess.