Perhaps I'm misunderstanding. Leveling up is really not difficult at all. But if by "character creation at higher levels" you mean starting as a high level character, yes that is a lot of character creation work all at once, and frankly, sometimes it's can be too much. Don't get me wrong, I'm usually game to enjoy some high level theory crafting, but I think sometimes when people get excited about a high level one shot they don't really appreciate how much time they're going to have to spend on character building to then briefly play a character they never really mechanically get the hang of.
I don't think the actual character building process needs streamlining, but I do think that inventory could use a rethink. Both giving out a simpler collection of random items players will likely never use at level 1 and having some sort of standard tables for inventory you might have rolling up a higher level character would make life easier. At the very least, and I know this is antithetical to WotC's "magic items are optional" claims, having some suggested tables for numbers and rarities of magic items PCs should have at various levels, along with a rough sense of how much wealth overall, would save groups some stress and time negotiating character creation in campaigns that don't start at very low level. And if that is something already buried somewhere in the DMG or whatever, sure that's fine, but it should really be in the PHB where it can more naturally be a touchstone for groups to work from, under whatever section there is for starting campaigns at higher levels.
