One way that non-combat flavor/abilities might work would be to extend backgrounds, which mostly give some proficiencies and/or languages. The PC can choose some additional background picks later on. This could be from their starting background or from a different one.

Example: The warlock I mentioned above started as a noble. However, due to actions in the game there were periods of time where criminal, entertainer, or spy might have been more appropriate. Rather than burning feats on non-combat things (which is unlikely for most players) having certain levels give background picks and pushing feats like Skilled, Linguist, or Observant to those would make sense. If they’re too much of a package, they could be broken up fairly easily.

I’ll do it to some degree, but feats are pretty darn rare so I’d really want to be sure I’m going to get bang for the buck. For instance, my warlock character took some rogue levels because of all the non-proficient thieving and scouting that was going on. It was nice having the ability to pick locks reasonably reliably. I don’t think it really made a huge difference with combat, but it was helpful and clearly worthwhile.

Anyway, that’s why I’d make it happen semi-automatically. It also means that you can reflect developments in the character well, either the past of the campaign (I went into this culture and picked up the language) or future (I’m going into this culture and want to pick up the language).

Out-of-combat utility is great, but no one wants to sacrifice an increase in combat power for for out-of-combat utility. That was the big mistake that 5e made with the first iteration of the Ranger: they loaded the class with flavor and wilderness skills, but its combat skills are inevitably going to trail behind the other martial classes (notwithstanding Hunter’s Mark).

Nicely written, absolutely correct. Feats are too precious to spend on something like this, unless you absolutely know the campaign will have tons of dungeon crawl. A lot of campaigns don’t. I will take feats that are non-combat but I have to be pretty amazingly sure I want it and trust the DM to make it worth my while.

In general what I think would help would be to have some “feats” show up as part of level advancement that are more for character color and simulate activities outside of the main thread in character. This could be done in lieu of downtime activities and might show up at certain levels, e.g., 1st, 6th, 11th, and 16th. I’m not quite sure what would work here but I’d prefer it to be more character-defining or non-combat than directly combat.

I can’t be the only person who read the bonus action element of Observant and immediately pictured how Sherlock Holmes has been portrayed in recent adaptations (e.g. by Cumberbatch and Downey) immediately reading the scene in a manner that would usually require a detailed investigation?

Note to self: remember to begin Summoning Dumpster Fire Elementals as a way to magically comment on the adventure…

It seems weird to say that a feat which is really useful for dungeon crawling is too narrow for a game which typically has a heavy reliance on dungeon crawling, but it’s true. Anything not directly useful for combat ends up feeling “too narrow” in D&D. Because combat is the one “pillar” of D&D where every character is involved more or less equally, it ends up taking priority in adventure design, and therefore in character building.

As much as “exploration” is one of the “pillars” of D&D game design, it’s very hard to design adventures and situations that allow every member of the party to get involved in the exploration side of things. It’s all too easy for the rogue to do all the scouting and spotting and trap-disarming, while the other players are just following along, occasionally making a saving throw when a trap-disarming goes bad.

It’s certainly possible to design dungeons and other environments which contain obstacles and hazards where all the players can participate (for example, a gate which requires a strong fighter, or a chasm which can only be crossed through magical assistance) but it’s a lot easier to just limit the number of traps, and make the adventure more combat-heavy. (The same challenge exists in social encounters. The “default” is for one party member to do all the talking, while the others stand mutely by. You need to work to involve the party’s low-charisma characters.)

And as for secret doors, they’re another design problem. As a DM, I don’t want to hinge an entire narrative on whether or not the players can find a secret door, so I rarely use them. And if you’re a player in a campaign where secret doors are rarely used, you’re probably not going to bother taking a feat that makes you better at finding them.

I wrote this background last week which is very specific and similar to the Delver feat.
http://www.tribality.com/2017/04/13/dungeoneer-background-dd-5e-for-yawning-portal/

Agree. A good balance is water-downed enough to not take away from a class, but good enough to let most PCs avoid a multiclass dip.

Yeah there are a number of things that are incorrect in 5E. Something like Dungeon Delver is just too situationally narrow to be attractive but might be useful in a very specific campaign.

While in general 5E is pretty clean, there are some broader issues. I did a bunch of analysis showing that weak saves really become problematic at high levels. It’s partly because strong saves are a bit too good relative to the DCs. It’s not a huge deal until you start hitting DCs around 20 but weak save characters basically can’t dig their way out of the hole with buffs or advantage.