I mean if anecdotal evidence is acceptable, in my current party, the highest-Strength character is our Cleric (16), who lacks Athletics. The Ranger is Dexterity-based, and neither the Bard or my Wizard have much Strength. The Monk has Str 12 and is proficient in Athletics, giving him a score slightly higher than the Cleric's (+4).
Any Strength challenges we've come across so far have either required multiple characters to begin with, or can benefit from Guidance and the Help Action. If more came up that we couldn't use Help for, we could prepare Enhance Ability, but it hasn't been needed yet.
There was one fight where Strength saves were quite dangerous, but somehow we survived it (we were facing wolf monsters that required a Str save with their bite or they knock you prone; they then had a bonus action attack against a prone target for hefty damage).
As for how often Dexterity comes up, several fights were made very easier due to winning initiative, the party has been lightning bolted three times now, and everyone but the Cleric relies on Dexterity for AC. Opening locked doors and bypassing traps has been important-both I and the Rogue have proficiency in Thieves' Tools, I'm skilled in Investigate, and the Monk has the best Perception in the party (+10 since he took a level of Rogue).
Carrying capacity hasn't really been an issue since we're using the basic 15 lbs. x Strength score rules. We did find a Bag of Holding, but it's really only used to carry coins, and we have way more money than we know quite what to do with at the moment.
A Strength+Athletics character has their uses, but we've been getting by without one, even in our recent fight with a lich where we had to use grapple to drag them away from a throne that protected them from spells.