You're never late, it's just that the spotlight has moved elsewhere. Goldsrc mapping is a niche activity in the niche of DIY games and indie gaming development.
The early to late 2000's mapmakers have moved on with their lives, and this community's structured (or not), polite (or not), involved(or not) conversations, as with most forums, were sucked into the Discord black hole.
As with every niche interest, there are always going to be people around to discuss with. Luckily, this community is, I'd say, still thriving.
But - to respond to your title question:
Is GoldSource still cool?
It depends. For us? Yes.
For 99% of the other people?
No. It's an anecdote most people will never care about.
If you want to be cool, follow the trends