Sure, PG's website (forums especially) is kinda quirky, but unique, and I find that I've gotten used to its quirkiness. So why bother changing the regular website. Now for mobiles and tablets, that's a separate issue that can be handled separately, way I see it.
I'm just curious, what you find quirky about the forums (aside from not being great on mobile). But let's assume you're on a desktop PC using the forums, what do you find weird about it, and what forum do you use that you don't find quirky? (just to clarify I'm asking specifically about the forums not the rest of the site).
I really only have one issue with the forums and that is they do not work well on mobile. I see you are on version 7.5.7. UBB claims that 7.6 pages are "mobile friendly" so a simple upgrade might address that, at least partially.
Being an old-timer who first enjoyed BBS using a Hayes 300 baud Smartmodem, I have been using these sorts of forums for many years. Therefore, I am quite comfortable with the forum here and find it to be adequate for the purpose at hand. With that said, it does look old and that will be a big turn-off to any younger demographics that PG may be interested in pursuing.