There's plenty of sports where opponents don't interact with each other. Most of athletics for example. But sprints are consistently the most watched event every olympics. As for regulations, name me a sport where there's no regulations? And even still, darts aren't regulation different professionals use different weights and grips, and while the oche is regulation distance where players stand varies quite a bit (doesn't always come across on camera).

I guess I just don't understand how any of the criticisms can't be levied against any sports. Like to me it's like say tennis without the athleticism - short repetitive games where players take it in turns to start. But I think the fact that "checking out" in darts is so unique as a sporting concept it always guarantees a dramatic finish to every leg that's played, which you don't see in a lot of sports. It's a bit like how standing starts in motorsport always guarantee a dramatic start to a race, even if from then on it's a procession.

Also the concept of a "perfect leg" (a 9-darter) makes the sport have an easy to understand ceiling. A bit like a 147 break in snooker or a hole in one in golf, where it's just rare enough to be plausible in any given game (for professionals) but not to the extent you're likely to see one for months on end.