There's been some discussion with this regarding other 5e systems, specifically Level Up A5E.I was reading an article by Justin Alexander roasting the 5e skill system, and arguing (among other things) that Expertise is bad because it breaks Bounded Accuracy, and Reliable Talent makes it worse. And with this, I disagree.
I think that Bounded Accuracy is excellent for combat's standard rolls: attack vs AC, and saving throw vs DC. That's when you need numbers that challenge the whole party: some characters may have a better chance than others, sure, but the d20 roll doesn't become irrelevant because this one is guaranteed to succeed and that one is doomed to fail.
But for otherwise interacting with the world, I actually don't think the numbers need to challenge the whole party. I think immersion and simulation (I like these!) are better served by making such challenges tricky. Occasionally they will be too easy for some, and/or too hard for others, depending on where the characters focused their training. And when that happens, it's up to the party to figure out ways to make up for it, to look for other, creative solutions rather than get stuck on a skill check that one or more of them are doomed to fail, and in the end to acknowledge that some tasks are suited for only some of them.
So maybe half the party auto-failing to scale that wall means they need to find another way in, or use their spells, or have the athletic ones climb up and throw down a knotted rope. That's good! It's a complication that requires a solution other than rolling a single check! Maybe only the Wizard (with 2024 rules) has a chance of making that extreme Arcana check about a long lost artifact. That's great! It makes sense and it's immersive, they should be the only one able to make it. And maybe, if your goal is to stealthily scout ahead, don't send forth the clanging armoured warriors, only send the sneaky rogues and rangers. That's fantastic! It's basic tactics! What's not to like?
[This technically applies both to 2014 and 2024 rules, though to my great chagrin 5.5 fully dropped the ball on the skill system. Honestly, I just picked the 2024 flair because I use an example from the new PHB.]
A5E uses an "expertise die," detailed below:
Expertise Dice
Some class features or traits grant you an expertise die for an attack roll or saving throw , or in a specific skill or tool proficiency. When you make a d20 roll with which you have gained an expertise die, roll 1d4 and add the number rolled to the result of your check.You can never roll more than one expertise die on the same roll. If another class feature or situation grants an expertise die that applies to the same roll, you don’t gain another die; instead, the size of the expertise die increases for that check, from 1d4 to 1d6, or 1d6 to 1d8. If you have a 1d8 expertise die on a check, further expertise dice have no effect.
If you have advantage or disadvantage at the same time as an expertise die, only the d20 is rolled twice, not the expertise die.
While advantage is most commonly used to represent circumstantial factors affecting a situation, expertise dice typically represent the particular training a character takes into the adventure
The expertise die is great by itself (flanking or high ground grants it in combat, characters get skill specialties that grant it on very specific checks for a skill), but in A5E so many character features grant flat Expertise to a skill that (in an extreme example) by level 4 you can have a +1d8 to all Stealth checks. Rogues are kings of this, (they can actually get up to a +1d12) but other classes can reach the max +1d8 expertise die without much cajoling.
So the question becomes, how do you make "realistic" DCs without making them so high that no one besides this PC could succeed at such a check? The problem is less common in 5e since it's ?mostly rogues? that get expertise.. but expertise at tier2 means a possible +11 to checks, which jumps even higher at later tiers. Couple this with other characters helping or providing Guidance and you have some really wonky possible numbers.
I do agree that characters should be good at what they specialize in, but it's still reasonable to want to challenge them at it.