Except most MADCS have methods of reengage and invulnerability. Half of them are resourceless and all of them have methods of fighting you and reducing counterplay. And almost all of them require autoattack damage and have crit interactions except Fiora.
The bruisers you listed have long animations or channels that eliminate your ability to DPS with attack speed or crit - a Renekton, Wukong, Jayce, etc. are spending half their time comboing spells without even getting a chance to autoattack (disregarding Jayce ranged W).
Meanwhile, literally all the MADCs do is autoattack.
Wukong has one spell that interrupts using basic attacks, his R, which is designed for team fight AoE DPS and a knockup. His E is a gap closer with an AS steroid, his Q is an attack reset with Armor Shred and bonus damage, and his W is not something he regularly uses in combat (and it doesn't interrupt him)
With Jayce, half of his abilities don't interrupt his attacks: Hammer form W, Cannon form W and E, and either form's R (yes, I will count his R, because it grants him bonus damage on his next attack). His Q in either form is meant to hit an escaping target (either closing the gap in Hammer form or firing a parting shot in Cannon form), and his Hammer E is an escape tool + anti-tank burst.
Renekton players always use Q between attacks, use his E to close the gap...the only spell that interrupts using basic attacks for damage is his W, which is a multi-attack that resets his attack timer. I guess the half-second casting time of his R could also count.
As a person who actually goes and plays these goddamn bruisers, each one of them bases a lot of their damage on basic attacks. The moment their rotation ends, it's all basic attacks. The only difference between these bruisers and most MADCs is that the bruisers have AD-scaling spells that aren't just attack resets, gap closers and steroids. Jayce has Lightning Field and Thundering Blow. Wukong has Decoy and Cyclone. Renekton has Cull the Meek. None of these invalidate the fact that they rely on basic attacks
The example you gave - Sion - is just false. Sion is kitable. No sticking method or means of invulnerability = no DPS. Every second Sion spends channeling W or casting other spells is a second he's not autoattacking (and wasting attack speed as a stat). In a perfect world he builds 0% attack speed and just tries to channel Q as hard as he can between every autoattack timer window.
"It doesn't work because you can kite him."
Implying that you can't kite other melee ADCs in any way, shape or form.
I haven't even gotten a chance to play the new Sion, and I know you've misunderstood his kit.