Many number if reasons split fins were ridiculed. It started with the tech, DIR, GUE, hoo-ra crowd who pretty much ripped them to the ground. They claimed they couldn’t be used effectively for heli turns, modified frog kicks, backing up, they silted everything out, etc.
They also came in all sorts of sissy colors like pink purple and hot yellow which according to them was ridiculous because everyone knows everything HAS to be black or it’s not real gear. Pool toys and tourist snorkelling gear is brightly colored, not real gear.
Splits are great for going forward doing the standard flutter kick. Some people can make them work for everything, but not many.
At the time, 99% of regular divers only did flutter kicking anyway so splits fit in well. Easy to kick, no leg cramping, enough power for regular easy diving, fashionable colors, what more do you want?
If there was no mainstreaming and leak over from the tech world into the regular scuba world on the internet they would have probably been accepted a little better. The rec scuba world was actually beginning to embrace them.
On top of that, there was also an old contingent of veterans that saw split fins as yet another gear solution to an ever increasing problem of more ordinary people getting into the sport and “watering it down”. Or put another way, a piece of gear designed for people too weak and without adequate leg strength and conditioning to use regular “manly” fins, which in they’re opinion those people probably shouldn’t even be diving anyway.
At the same time, Jets were experiencing a rebirth if popularity through the tech world. Remember, there were several times when Jets were Almost discontinued and considered obsolete by SP.
As I remember, there was an epic cage match between the two fins on Scubaboard that went on for several years. Both fins got pretty bloodied up, but the Jets won (I guess). I don’t see splits much anymore in dive shops, more paddle fins, and Jets are still hanging on their own peg so I guess they did win.
I’ve tried many fins and my favorite split fins were the SP split jets. I liked those better than the Apollo Bio Fins which were too noodley for me.
I thought split jets were actually better than Sea Wing Nova’s, and for flutter kicking they blew away standard Jets. Regular Jets are good for every kick EXCEPT flutter kicking.
My personal favorite currently for most power and best overall flutter kicking efficiency are freediving fins.
Fin debates have gotten so heated on scubaboard that people have been banned over it.