Unpopular opinion: You should actually need to buy AP/AD to do massive damage.
AD fighter/juggernaut/etc? They might have sorta-ish high bases depending, but if they want their damage to stay relevant, they'll need AD. AP Mages/APCs (Azir/Cass/etc)/juggernauts (Mordekaiser, etc)? They'll need a good bit of AP and usually Void Staff later. ADC? lul build full crit/AS with Zeal evolutions, get a massive chunk of MS bonuses, rely almost entirely on autoattacks and base AD, but shred through just about anyone anyways and have constant kiting capability through the gift of being ranged
Like sure, even with the crit builds, IE and/or ER is usually built as well which gives a decent chunk of AD, as well as LDR/MR in lategame. Except even if IE/ER had no AD just like the Zeal evolutions, ADCs would still melt people in seconds.
I'm all fine with building full glass cannon via stats for massive damage (read: assassins/non-health building mages/full AD fighters/etc). But when a class can literally just build crit chance and attack speed (Runaan's first item for instance) and rely almost entirely on their base AD-derived ranged autoattacks and do more damage faster, it's mildly irritating.
But hey, I guess that's just me being Bronze 4 and trash at the game. shrug

WHAT?!?!?!