This is all much more likely to happen outside of the public gaze.
And so I think you are looking not for a website but for a person, or perhaps a website that helps gather such people - and somehow keeps out those who claim to be all of the above but are fooling themselves or the rest of us.
Where do you find good people? There’s probably a market for an “intellectual dating site”.
The sparring and point scoring that charaterizes a lot of spirited debate depends on a kind of collegiality that I think is an artifact of a former time. You can't engage in that with (or even near) someone whose recieved identity is founded on being a reaction to that specific collegiality, but even still I've come to think it's not even the "Them," that ended it.
Debate itself is a kind of intellectual leisure that you don't want to flash around too much because what social media did was put us all all in an arena that was previously reserved for elite level competition, where players play and commentators comment. The way people signal their membership in the players' club is by not commenting. If you're talking, you probably aren't in the game, and if you are you're probably losing. I have been writing almost as long as I've been in tech so public discourse is my idea of fun, and the choice to take on that player/commentator opportunity cost was personal, but the reason you aren't seeing great online debate is because what it comes down to is, for the people you want to hear from most, it just isn't worth it.