The Barry Gray music plus the OTT wardrobes plus the absurdity of Straker's job & HQ-bunker make an irresistible combination.

FWIW: apparently Sylvia Anderson sincerely thought that wigs were the future.

I'm still a fan. I rewatched a few years ago. It's darker than I remember and there are sexier elements I completely missed as a kid. Some of the episode themes - like racism - were far ahead of their time.

Of course it's dated now, but I don't think it's more ridiculous than today's superhero franchises

If you compare to other British 1970s TV SF, like Dr Who, it was a remarkable effort.