Crimson Longinus
Legend
I'll take a bit of a stab at this, though I'm actually kind of two minds here.
The new edition of Alternity has a design feature where every character has to have at least one skill in each of six categories of skills. (I want to say its vehicles, tech, social interaction, knowledge, ranged combat, and melee combat). Why is that?
So you can be sure no one is entirely left out when the game moves into a certain kind of situation, a situation that may be time consuming, they have at least some potential ability to participate.
There were serious objections to this. But I think part of it was the same issue of people not looking at it kind of the wrong way (though I think you've mentioned both in the past). The purpose is not to make everyone good at everything; its to make sure no one is really bad at anything.
Now, that can bother you too, on a character representation/simulation grounds. As the Alternity 2e people said, why should a scientist or engineer automatically have combat skills? The answer is, on those grounds, there's no reason they should. You can rationalize it easily enough if you want to, but it isn't a default given.
But, and I know this sort of thing bothers some people a lot, a large number of games really don't care about those grounds. They're making design decisions on gameplay grounds, and on those grounds, most people don't find it fun to feel useless, even if they're the boss in other contexts. They'd rather be able to at least contribute in almost everything.
But you also have games that are kind of not committed to either approach, and that can end up being kind of a problem for everyone.
Edit: And of course Ezo has an important point above; the limitations of class games can produce results that seem, bluntly, irrational in terms of channelling growth in very narrow ways that don't necessarily serve either the fiction nor the game all that well.
I get the Alternity approach, but I don't think the suggestions here are similar, even though they might appear to be trying to solve a similar issue. It seems in Alternity the characters still can be bad at individual skills, they are just not completely useless in any facets of the game. In 5e it would be similar if all characters were always proficient in at least one social skill and one exploration skill (everyone is already "proficient" in combat.)
What I don't see as good idea is the homogenisation, where the difference between being skilled and not being skilled in certain things is erodes. 5e proficiency bonus is already pretty meagre (hence the topic of the thread,) but effectively halving that so that difference between skilled and unskilled is just paltry 1-3 points? At that point I'm not sure there is much point even bothering with assigning skills.