Despite how fresh Legend was at that time, it was a downfall after the classic series.
Let's start with stories and dialogues in Tomb Raider games. They were always bad and cring. But the good thing about classic games is that there was almost little story, they were mostly about the gameplay and levels. Legend, like any other modern game, tries to show as much movie as possible. So it is not just bad sometimes anymore, it is bad almost all the time!
Of course, the gameplay was also simplified for a new generation. It fixed many issues of the original game but also lost the core: now it is just a linear action game with some one-room puzzles instead of adventure where every level is one giant puzzle you have to investigate and solve.
For sure, many people will like dumb action more but as the successor of previous games it was a large step backward.

I remember how magazines were writing at that time: well, people were starting to get tired of Tomb Raider games since they were not changed, and Eidos sold us the same game again and again.
Just remind you that professional reviewers never play games and tell random words about everything.
While Tomb Raider 1 was a perfect game, and Tomb Raider 2 was action-based DLC with fresh ideas in levels, Tomb Raider 3 is sadistic torture for a healthy mind.
I had a good first impression, and I remember from being a kid how different stories, levels, and costumes in this one. So I thought: ok, probably at the end of the day I will give it good review with a mark "can't recommend but I loved it".
I still can't recommend it and I don't love it. I dropped it right before last chapter, or I should say I rage-quitted it and going to never touch this piece again.
People often remember how brutal traps are in here, there are many places where the game doesn't give a chance to the player and one-shot him just because it is funny I believe. It is not a big problem since we can save game any time.
But endless backtracking and total lack of sense or logic, these things killed me before I completed it.
And this makes me mad. On paper, Tomb Raider 3 is great, it has enough good ideas and features, and it felt different from previous entries. But it is insanely painful to play, to rinse and repeat many areas, to wander around without any clue about what the last button opened.

Despite the game being awful in many areas I would like to mention what I found here is well made even compared to the following iterations (Dark Souls/Bloodborne/Sekiro).
- Levels and bosses are more puzzles than fighting challenges. I feel every next game focuses more on fights and action challenges since this is what the audience wants. Demon Souls is more about finding required items and using them. The worst thing about it is some items are almost impossible to find without guides so the game feels unfair and annoying sometimes.
- Art design is great, and I found it much more appealing than in the following games.
- The story and events happen in a much smaller scope, and I like that story is simple and understandable. Still some characters look completely underdeveloped.