I agree with you that RTR and Khans are better, more carefully thought out sets, but they are a bit, how should I put this, safe. They aren't as raw as the original Ravnica and Shards. Let me explain this.
Khans for instance, with morphs as a mechanic, there was no way you could screw up your draft (unless you tried to force goblin slide or something). There are more than enough playables that actually made deckbuilding difficult at times. Morphs being ever present also meant less strain on the mana and curve. Everything was designed so you could play morphs on turn three. And nothing had an unmorph cost below five mana with toughness higher than two, which played into this. It's all very meticulously designed. Being an Izzet aficionado, I felt it wasn't brilliant in a crazy way. It didn't reward skill enough. There are few unmorph triggers unlike in Onslaught. The morphs were generally bigger creatures with no opportunity costs. It was laden with bombs. Comparing uncommons and rares isn't fair, but Khans had a vast number of bombs. So many that it warped drafts. Like there was no way to come back after your opponent plays Savage Knuckleblade on turn three while you're holding a bunch of morphs. Savage indeed.
RTR on the other hand was too restricted compared to the original Ravnica. And the bombs in RTR were much worse. Compare Loxodon Hierarch with Loxodon Smiter. They're both 4/4s with marginal abilities but the Smiter costs one mana less which is huge in limited. At uncommon level, there were the guildmages which were completely busted in the right deck. The original Ravnica's guildmages were mostly just playable apart from Selesnya. The original Ravnica actually had a lot of bad cards at all rarities. Why is it despite that lauded as one of the best limited formats? Because it rewards skill. It's satisfying and therefore fun to draft Ravnica. Having karoo lands and signets at common helped a lot as they lowered the chances of mana screws and floods.
I prefer formats where bombs aren't numerous (because I rarily open them.) They're a part of the variance in the game, but please, no more 4/4s with upside for three mana that are piss easy to cast.