Are you aware that by using the style chooser in the bottom left corner of the website, you can reset the whole site to a non "RPF corporate identity" look? You'll even loose the top logo, which can't be what you want... Nevertheless maybe this style selection is the key to a darkmode / RPF retro design?
I must say, that the readability of the new site is far worse than before, mainly because there's no color difference / boundary between ads or screenshots - same goes for the tiny line separating different posts. I guess this could be changed by minimal corrections to the background color...
What I also noticed is the new design always shows the images in full, while these were thumbnails in the past... This comes down to personal preference in the end, but in my opinion this also helped a lot with readability. Any chance to add a preference setting for this?
Halifax post above is an excellent example for both, btw.
Regarding the new RPF design, from a perfectionist point of view some of the colors does not really fit IMO... E.g. the "upload file" button down below when posting. Never noticed this on the old site... Same goes with the style of the premium banners next to the avatars, these don't match the overall minimalistic design. Might seem pretty crazy to mention these details, but they will add up to how much you like a website or not.
The whole site is way faster now, sadly most of this performance upgrade is compensated by the time lost due to the worse readability and the missing top navigation bar... Just my thoughts, maybe some will find their way into further improvements!