Ruin Explorer
Legend
I mean, what you're describing is a 6E, unless 2E was also a "1.5" but ignoring that...Let's assume that we will, indeed, see revised core rulebooks in 2024, a proverbial "5.5." Let's also assume that it won't be more than 5.5, and maybe more like 5.3-5.4...the key being backwards compatible.
The question: What aspect of the core rules do you feel is most in need of revision? If you could ask the folks at WotC to revise one area, what would it be?
For myself, I've played 5E too sporadically over the years to feel like I know the system inside and out enough to offer a super educated opinion, but my first thought is classes. Maybe I'm biased because ranger is my favorite, or at least default, class, but I'd like to see them strengthen some of the weaker ones (ranger, monk, sorcerer), and without requiring a subclass to do so.
It is probably too large of a change for even 5.5, but I'd like to see how a slightly less bounded accuracy would look, with Proficiency Bonus going up to +10 at 20th level rather than +6. I like bounded accuracy, but wonder if it is too bounded. It just strikes me as odd that a 1st level fighter with 20 STR has a base +7 to hit, while a 20th level fighter with 20 STR is only +11. I know: class features, feats and magic items and all that. But, still.
You?
Obviously there are things which literally must change:
Lineage and that general approach have to replace race
Alignment has to be downplayed further
Design has to move away from the "apology mode" of 2014 towards "we have 50m+ players" mode of 2021.
Tasha's choices built in to classes - making them the default in many cases.
Everything else is semi-optional:
FR should go as default setting, imho. Don't have a default setting or use a Nentir Vale strategy or even licence Wildemount in perpetuity if they'll let you for a reasonable price.
Ranger needs to be reworked and finalized.
Re-jig Sorcerer to be pure spell points. Alternatively, remove him from the PHB and replace him with Psion or something.
Completely re-do healing and grittiness mechanics. Kill Hit Dice, they don't interact with much so it won't matter much. Replace them with something very like System Strain from Worlds Without Number, and actually make healing spells interact with it (it's very simple to do so).
Change short rests to 10 or 15 minutes. Long rests remain where they are but don't automatically set you to full HP.
Re-write the DMG completely. Top to bottom. Massively improve the quality of advice - nothing in the DMG stands up to the quality of advice in either DMG2 from 4E (!!!) or VRGtR which just came out. Completely replace all optional rules in the DMG with actually-playtested, actually-sane rules, none of this "I came up with it on a break to fill a requirement" stuff that we have now.
Archetype choice should be the same level for everyone. Probably 2. With the advice that experienced players can just start at L2. None of this nonsense where some people start with a theme etc. at L1 and others can't have it until L3.
Prob more thoughts later, these are the first that occur.