That is entirely out of the hands of the people who run Talkbass.
You would have to convince the developers of the platform to allow that kind of styling in their product, and then TB management to make use of those features. It is more complex than a simple reskinning.
I think the look and feel of this site is now more in line with what is seen as the current state of the art. So you are trying to convince someone to “make it worse” in their mind.
Maybe just try embracing change and putting a positive spin on it. Within a few weeks you will be used to it. The chance of you talking someone into 10’s of thousands of dollars of software dev work, if not more, is slim to none.