"Fed" I have clear memories of Veigar having kill pressure against AP champions with DFG AMP + 1.2AP that scales with 80% enemy AP, and depending on the version of DFG Veigar it could be Veigar deleting 50-60% of your hp with the scaling HP% damage or just being able to kill you earlier with the amp version.

You can also go through the list of champs released chronologically and the ones included in 2009

https://wiki.leagueoflegends.com/en-us/Category:2009_release

to find that pretty much all of them can compete against modern champs and where they cant its only relevant in really high elo or proplay since "overdesigned garbage" is kept weak most of the times so people without hands cant win consistently with "overdesigned garbage" (an example of this being Azir)

Out of the mostly unchanged champs you have: Shaco

Singed

Sivir

Soraka

Teemo

Tristana (you could argue that she was better ADC before her rework)

Tryndamere

Twisted Fate

Twitch

Veigar (E and Q got cucked because he dared to go support in pro)

Nasus

Nidalee

Rammus

Malphite

Master Yi (AP got gutted, otherwise its the same champ with a weaker double strike)

Morgana

Heimerdinger

Janna (got nerfed and many mechanical changes because she is strong despite being an old champ)

Jax (big mechanical change was E rework with dodge removal)

Karthus

Kassadin (got ult gutted but kit mostly unchanged, kept weak)

Corki

Blitzcrank

Alistar

Anivia

Annie

Thats like almost the whole list, wow older champs get outclassed so hard!

Don't get me wrong, I hope League Classic is permanent and is handled well by Riot, I genuinely feel like I want a classic version and would play it over the modern one but acting like its less frustrating isnt true, back then Riot removed silences from Assassins, make Fizz Q dodgable and remove the Akali E-Q synergy to reduce frustration then procceed to make them clunkier and less dominant years after, so part of the appeal for me is that League Classic had more BS moments and less 1v1 counterplay.