>30 years ago was 1990

Your overall point is valid, though I think you'll find that this particular calculation isn't correct. (The current year ends in a 6 so 30 years ago also ends in a 6.)

However, I just did a quick search for the Doom release date, which was 1993 and the original system requirements which is Memory (RAM): 4 MB and Processor (CPU): Intel 486DX (66 MHz).[1] So in terms of RAM this is 16x as much and in terms of MHz it's 6x faster on one of the cores. So it's definitely desktop-class for 1993. (33 years ago). As you state, it's much faster than desktop class in 1990.

[1] I only just looked at Google's AI summary, maybe it's wrong: https://imgur.com/a/LbhAmGp