Was thinking about it a few days ago but I think it's pretty cool that Clefable has managed to be good in Smogon's competitive OU standard metagame for several generations straight, all the way back from Gen 4 to now in Gen 9, six generations, even if it wasn't always actually OU by usage during that time. It's really neat for Clefable in particular to be as good as it is because in the face of generational power creep and more aggressively min-maxed Pokemon (with their best stats being well above 130) dominating the higher tiers and the official VGC metagames, Clefable is pretty unique in that it's a Gen 1 Pokemon, aka an oldie from the beginning, and like most of them it has an average, jack-of-all-trades, master-of-none stat build, and in Clefable's case not a single stat above 100, with its two highest stat values being at 95. And yet in spite of that, which would normally be a downside for most Gen 1 mons and has led to them being power crept, Clefable on the other hand has endured the test of time because its combination of amazing movepool, amazing abilities, and in later gens being pure Fairy-type mean it offers so much to the table and does the jobs it is capable of doing really well, with its well-rounded, not min-maxed stat build actually ironically working in its favor.
While it's not as prominent in VGC there's still another funny thing to note there and that's the fact that Clefairy has seen a strong amount of niche use in VGC as a Follow Me bot, which is another plus in the line's favor: a pre-evo, one with really bad stats in a vacuum no less, manages to have just the right tools to find a niche even in modern power crept VGC metagames thanks to what it brings to the table.
The Clefairy line is a real winner of the OGs, even if it doesn't look all that impressive in a vacuum, and a prime case where the original design ethos of the Gen 1 mons, which is decent, well rounded stats but not min-maxed, while having an insanely wide movepool with almost every technique imaginable, actually became a strength for Clefable rather than a weakness, thanks to its combination of typing, abilities, and its well-rounded stats allowing it to make effective and useful combinations of tools from its wide movepool that give it a niche. I think that's pretty damn cool.