"Not Ultra Rapid Fire:
"Cooldowns increased by 200%, mana regen reduced by 50%, summoners spells disabled, death timers TRIPLED.... and +5000% damage to dinosaurs!"
I would have laughed myself sick if they'd done this (though I would mainly be laughing at the agonized wailing and rage of those that I had been forced to see spamming the comments to "Bring URF back!!!!!" every time I scrolled down for a year now, revenge is sweet).
Funny thing is, that actually sounds waaaay more interesting than all these other featured game modes. More strategic, more tedious... yes, perhaps even more boring, I'll admit that... but interesting. Everyone would fear wasting ultimates, worry about all-in engages with no flash to get out, play safe to avoid dying. It would become all about strategic map control and gaining objectives like dragon and baron to shove down turrets from relative safety, with last-ditch all-ins from losing teams sometimes pulling off miracle comebacks by acing enemy teams that couldn't flash away and then had their bases wrecked during the increased death timers.
It would be interesting for a bit, but if played for more than, say, I don't know, a week, would become more stressful than fun as the initial interest wore off. Gosh, an interesting idea that would allow people to play the game in an entirely new way to maintain interest in League among it's longstanding fanbase but that no one would really want to see in the long-term... that almost sounds like what a featured game mode is for! (Not that I'm naive enough to think this would ever happen, not that I'm even so much as suggesting this, and not that anyone other >1% of players would actually appreciate it, but just pointing out the irony.)
Honestly, I wouldn't really have even enjoyed NURF myself as I described it, but if it had been released sometime before I'd become completely blasé about featured game modes entirely I might have tried it. By now, though, it'd take something REALLY intriguing to me or sounding particularly fun (I did not enjoy the original URF, and don't feel compelled to even try the "balanced" one) to move me from my disinterest to actually try a new featured game mode (Poro King accomplished that actually, and I did like it, if you want an example of something I would consider a success, because I'm not just a killjoy lol).