They’re working off the concepts for the first movie that they weren’t able to build upon due to technichal limits.
This is basically what tron would’ve looked like had computers been a bit better.
Plus the world is more organic simply because Flynn has been in there for 20 years. That’s 20 years of NATURAL evolution in a computer server (so it’s EXTRA fucking fast) because Flynn was the catalyst.
And sure it doesn’t look EXACTLY the same, but anyone whose seen the film, then this trailer (without title or mention of names) would know it’s tron.
But your quote DOES bring up another point. HL2 doesn’t make you feel nostalgic about HL1, correct? Because it’s a sequel. It’s purpose is to be a continuation. Not a remake whose purpose is to bring the old to the new and the new to the old.
Tron Legacy is a sequel. There’s no need for nostalgia.