The game is a bajillion years old, new players don't like it because it's dated.
A lot of the rage over HL2 was the physics engine, that was jizzworthy back then. Like the first time you played you'd probably spend a good 20 minutes just playing with cans and shooting them.
It's still a great game as far as the narrative and such, characters and level design are brilliant, but it can often feel a bit bland when you don't get the same wow-factor from the graphics and physics.
Edit:
One more thing, HL can also fall short of the expectations of modern-FPS fans because so many FPS games these days are just cover, run and shoot, while Half Life often breaks up the combat with platforming, physics puzzles and driving sections. It might help to not think of it as purely an FPS game, but a mix of genre's; Personally I much prefer the mix of genre's.
A lot of the rage over HL2 was the physics engine, that was jizzworthy back then. Like the first time you played you'd probably spend a good 20 minutes just playing with cans and shooting them.
It's still a great game as far as the narrative and such, characters and level design are brilliant, but it can often feel a bit bland when you don't get the same wow-factor from the graphics and physics.
Edit:
One more thing, HL can also fall short of the expectations of modern-FPS fans because so many FPS games these days are just cover, run and shoot, while Half Life often breaks up the combat with platforming, physics puzzles and driving sections. It might help to not think of it as purely an FPS game, but a mix of genre's; Personally I much prefer the mix of genre's.