I thought champions who had no resources were supposed to have high cool downs?
Auto-attacks are manaless with low cooldowns.
Manaless champions tend to have abilities that feel more like auto-attacks than abilities.
Also - mana is generally an ammo system to keep front-loading 10 seconds of damage into 1 second in check.
Riven's QWER combo is actually R + W + E + Q + Q + Q + R, none of those abilities can be cast at the same time, and she probably wants to fit auto-attacks in there to make use of her passive.
Mana costs usually get bigger and bigger when you move further and further away from the AA AA AA AA AA AA style of play - LeBlanc and Veigar have high costs because they can front load 10 seconds of damage into an instant. Riven front-loads, like, 10 seconds of damage in 7 seconds.
Or if you're super solid at animation canceling - you can do that with any champion's combo and auto-attacks themselves, leaving Riven proaportionally slower at unloading her combo to most you compare her to.
So - exact opposite. Manaless is supposed to mean ability spam, you just have to spam a lot of abilities to match the power a mana-using champion has.
You have like....a 3 second window to where she cant cast anything and thats it.
Again, she's a glorified auto-attacker. Champions like Tryndamere and Cait always have something nasty off cooldown.
Once she gets 40% cdr she's impossible to duel/chase or anything.
You can easily beat Riven in a duel with any champion that has any buisness trying to force a 1v1.
Fighters and Assassins tend to be the only archetypes where there end-game involves forcing 1v1 duels though, most champions win by being awesome in a team fight.
And Riven isn't that awesome in team-fights.
She's supposed to be a fighter but shes more of an assassin.
She's listed as a fighter/assassin, and she plays more like a fighter than most fighter/assassins. Riven is more about endurance than burst, where a fighter/assassin like Jax, Aatrox, Fiora, Yi, Xin, or Pantheon, etc. is going to bleed more into the assassin side than Riven.
I mean, I'd even give Vi better assassination potential than Riven.
Assassin is mostly burst, fighter sustained DPS in melee, and Riven is about as sustained DPS in melee as you can get without being limited to auto-attacking alone.
I mean - at 200 AD Riven's Broken Wings is only going to do 210 damage, where anyone ever auto-attacking with 200 AD is going to do 200 damage. And maybe 500 damage with an IE crit on those autos.