The question isn't if you see a big difference between Athletics and Acrobatics. The question is if MECHANICALLY you see a big difference between Athletics and Acrobatics that aren't covered by the differences in ability scores? Many of the checks needed (escaping grapples, spells, etc.) right now can use either. And a bunch should. For example, right now someone with expertise in acrobatics with a 20 DEX has no indication that they can climb. That's STR (Athletics). I've literally had two different players curse that their uber-agile elves most likely would fail at climbing a tree or wall. This is double jeopardy. Just shy of half the people who could detect something will never get a roll, and of those that get a role many will still fail. Use one or the other, otherwise you are drastically changing the success/fail percentages in a way that messes up the math of the system.
"I've literally had two different players curse that their uber-agile elves most likely would fail at climbing a tree or wall."
First, climbing by default doesnt requir a check. Isnt it half speed unless it's difficult? What kind of tree climbing are we talking about?
But, the system already allows the GM to allow/call-for a Dex (Athletics) check if they think it's appropriate.
So your higher dex elf wanting to climb a tree just has to describe his actions in a way that leads the GM to decide (for a difficult climb) that Dex (Athletics ) is the appropriate call.
Second, the two different proficiencies divide the types of training - the kinds of things a character has experience in. The player can choose the ones appropriate to their character. If your elf is supposed to be very good at climbing, why didnt you take athletics since that is the skill that includes climbing? Complaints like thst early on would likely be met with "ok so you wanna swap out what for what in your background?" In between games
Third, to me, when a player is unhappy at the success/fail etc in a game they are playing in, that's more indicative of a disconnect between the GM depiction and their understanding. Did the GM not describe and set the scene with the tree up in a way that they understand why a check is even needed and why it's so difficult for them to succeed? In my gsmes, unless there are surprises or unknowns, my players tend to know the DC before attempting a task due to my efforts st being not just descriptive but informative in my depictions of the situations.
Fourth, design...
I would generally be against creating an overly broad "lets get physical" mega-skill myself when I see nature, religion, etc snd persuasion, deception, intimidate perform etc broken down as they are. It seem inconsistent with the rest.
Consider...
Physical stuff
Ability scores tested Str or Dex (rarely con)
Skills athletics, acrobatics, stealth, sleight hand and sometimes performance maybe?
Brainy stuff
Abilities tested Int Wis
Religion, Arcana, History, nature, investigation, Medicine (insight arguably)
Social stuff
Ability tested Cha or Wis (possibly Int)
Deception, Persuasion, Intimidation, insight, (investigation useful)
What's left - survival, animal handling and perception?
Regardless of where you put those, it really doesnt look like the physical set is somehow plagued by excessive sub-dividing and compared to the rest in need of consolidation.