True.
Warlock is the hardest class to screw up. Partially why it is the baseline.
But the warlock still has way too many choices to be considered a simple class.
The simple arcane caster would pretty much be a warlock with the choices picked and prebuilt into the class.
Idk i dont think the simple caster needs to be
dirt simple, just on part with fighters and barbarians.
So like, assume the EB cantrips, and pair the Pact invocations with automatic other invications at appropriate levels, and maybe shorten the spell list, and i would be pretty happy.
Oh and make it an unarmored defense class.
So at level 1 or two you pick a Pact and automatically get the followup invocations at level 5+, with only a few other invocations as you level, a spell list that is only about twice as many spell as the number you know, and make EB more flexible but it is your only attack cantrip. Make Hex a class feature called Warlock's Curse.
Also, Blade and Chain would lean on EB. Blade would turn it into a melee attack, and Chain lets you cast EB through the familiar. Tome increases complxity by giving more cantrips and more spells both from a large list.
Simple but flexible, and then subclasses can range from simple to complex, with clear guidance about how complex they are in play.