I think that's a valid concern. BUT I do think 5e, particularly the DMG, could be MUCH better organized and explained.
The system isn't THAT complicated but you wouldn't know it by the way the DMG is organized! If you don't know what you're looking for, good luck finding it!
Better organization, better examples of the play loop and overall better presentation in the DMG would essentially simply the game by showing it's not as complicated as it appears.
Unfortunately... I have the strong feeling that WotC is again too focused on updating the
rules and the
narrative of the game for the 50th year edition, and they aren't talking much about improving the organization/explanation of the books. If you ask them, sure they'll say it's very important but I would bet anything that the next version of core books will still have 90% of the issues related to presentation.
Back to your older comment, complexity is not only in character choices.
(1) Surely, the more
choices at character building and levelling up are part of the complexity, but these are supposed to be a matter of concern only once every few sessions, and can be dealt with all the time you have
between sessions to avoid sluggish.
(2) Definitely of bigger concern are
in-game character's choices. Having 20 different possible actions (abilities, spells etc) to choose from makes the game clearly more complex than having 2-3 only.
(3) There is finally
action resolution which plays IMO the biggest part in increasing complexity. This includes abilities that have intrinsically long rules, such as spells with many variables to choose before even casting and/or details to check before figuring out how they went. And it also includes exception-based mechanics...
Think for example of bonus actions. They are an exception to the default "1 action + 1 move" per turn. Not everyone has bonus actions to do, technically everyone can do 2WF but it is not worth without some dedicated ability, however a character with a free hand could start thinking why not just popping out a dagger for an extra attack and put it back by exploiting the one-free-object-interaction rule (which is supposed to be a kind of "green card rule" and is already likely to trigger some discussion... see how complexity is already creeping in?). Then you need to actually know how light, regular and heavy weapons work or not with 2WF, and what (exceptional) abilities you might have that modify the situation. But let's say you instead have a bonus action spell you cast, then you could think you're able to cast another with your regular action but it can only cast a cantrip. So you have a mechanic that works as an exception with a built-in exception-of-an-exception, or whatever you want to call it.
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The game could be better, but instead of trying to change the mechanics (which is... complicated!) I still stand for my previous opinion that it is easier to IGNORE options or rules.
An obvious way to lessen problems 1 and 2 is play the game at lower levels. Don't go to higher levels until everyone is comfortable with more complexity.
Then, I find that PHB races have too much baggage at once. I don't like that Human is the only low-complexity option, but since I normally play with casuals I always let them narratively play any race while using human stats (variant or not) to stay simple. But it is still missing something more unique for each non-human so at least I am allowing Xanathar racial feats to be taken with this option, and I'm thinking of also letting them choose one of their race core PHB trait in place of the feat, and swap the bonus skill with darkvision if appropriate. The result is simpler than the PHB version of each race but the price to pay is more time spent at character creation.
Then for everything else, the best a DM can do is figuring out herself what are the low-complexity options and suggest them to players who are afraid of complexity. Compile a list of simplest spells by class, identify the simplest class/subclasse features choice (when they have to be selected) etc and only show these to that kind of players so that they both have a more limited set of choices, and they will be the easiest ones during play.