TL;DR – Ask yourself this: Did you see this “issue” with graphics before the comments in chat? If not, then it is quite likely that the hyper-focus created by the criticism has made the graphics appear worse than they are [thanks, psychology]. And from your post, it seems like that is exactly when you started having issues, not prior.
Let me make sure I understand: You were watching a streamer, and the chat said something, which has caused you to become distraught over the graphics – correct? Have you played the game yourself recently? Have you ensured the streamer did not lower the graphics? Did you consider what you think (and thought) about the game, rather than falling into lock-step with what chat thought?
What I have seen looks nothing like Runescape ~1999, although I did just watch a recorded stream where the streamer later mentioned in the comments that they had lowered the graphics before streaming. I do not agree with the chat, and I do not agree with the idea of stressing about an aspect of the game solely because some people had a negative opinion. There will always be negative opinions about everything, no matter how good or bad. Do no allow the winds of the internet to change how you feel about a project you backed.
The graphics are not 2020-level graphics that the newest cards are going to overheat trying to render out, but neither are they near 1999- or even 2005-level graphics. IMO, from what I have seen, the game looks decent enough for the style of game it is.