Not that I agree with him, but what about his complaint was hard to follow?
5e casters get significantly fewer spell slots than in, say, d20. (4e is just different)
5e casters get fewer slots than even a Wizard (let alone a Sorcerer) in 3.x, mainly due to not getting bonus slots for high caster stat, and, at high level, to getting fewer 6th+ level slots. But, aside from that, they still don't start with 1 slot at 1st level like a 1e magic-user, and, while they may not get as many slots at every level, they do get to cast them spontaneously, and are not subject to losing slots when interrupted, so they don't /waste/ as many slots as TSR-era casters tended to.
(of course, 4e had far fewer slots than other eds, but it made up for it with at-wills and short-rest-recharge slots, in addition to the handful of daily slots - 5e gives casters as many or more at-will attack cantrips as 4e, some short-rest-recharge slot mechanics, and daily slots more in keeping with earlier eds.)
Given all that, 5e is arguably the best of all possible editions for casters, overall.
Let's instead discuss the topic: Personally I don't agree with the argument "high level spells are not powerful enough to warrant so few slots". Save DC auto increase. Magic items and scrolls. No, casters gain plenty of slots (assuming default treasure, or as published in official modules), just not ridiculously many.
Agreed. Heck, with saves scaling with character level, it could be argued that low-level spells are potentially too powerful to warrant so many slots...
