Actually, it was worse than that; I had no agency. For example, I recall spotting an interesting nook in one level, investigating where it went, then doubling back to see where the main path went. But then I found that the main path was blocked, and in fact the only way forward was the interesting nook. It wasn't the first time this happened; but the cumulative effect was that it completely broke the game for me, because it removed any incentive I had to pay attention to my surroundings - I realized I would be beaten into submission by the direction of the game, with heavy-handed clues bludgeoning me to go the approved path.
I saw the levels like evented puppet boxes. Early on in HL2, there's a bit where you pop out of a sewer, and around a corner to the right, there's a bunch of guys on a ledge shooting at you. It is impossible to kill them without going all the way around the corner and into another tunnel to "cleverly" pop up behind them. After a couple of hours, you could almost see the bounding boxes of the script triggers, it was so predictable. The forced nature of the encouters were quite different from the action bubbles of HL1.
Deus Ex had moved the art so far forward, while HL2 was stuck in the past.
HL1 was what I might call a tactical bubble game. There's one action scene followed by another, with the paths in between fairly linear. But the action bubbles themselves were reasonably open to different tactics, and especially when fighting the black ops enemies, fun. But it's a very dated by today's standards, because Freeman never talks, and indeed, has no agency himself.
So I feel justified in calling CoD a shooter on rails, because when I talk about agency, I mean a lot more than what those games give you. You do literally have control over movement, but it's an illusion; you have no choice but to go where the directors force you to go, and to the extent that you break out of your box, you're finding bugs in the experience.