If by "not (neo-)Vancian" you mean "not using the standard spellcaster progression," then I agree*; but there are literally infinite ways to build a caster who doesn't use the standard progression. The way that was chosen for the warlock would fit the sorcerer much better IMO.To me the warlock feels perfect how it is. Warlock magic is literally your patron cheating the system to get you magic so it should not be Vancian or NeoVancian.
If it were up to me, I'd give the warlock a couple more top-level spell slots and remove the focus on at-will abilities. Then I'd give them the ability to regain spell slots by spending hit dice (or hit points if out of hit dice), supplemented with other options specific to the pact. The idea would be to center the warlock on making dangerous sacrifices for power, with the mechanics reinforcing the concept of the class.
*All spellcasters in 5E include a neo-Vancian component -- a set of spell slots, usable for any spell known/prepared, which recover after a period of rest. All of them also have non-Vancian magical abilities usable at will, including but not limited to cantrips. The warlock is the same, it just has faster recovery time, fewer spell slots, and more of its power allocated to the at-will options.