Blindsight or Tremorsense are the only abilities that let you 'see' through fog or smoke.

I'll spare you my original overly-off-topic explanation; suffice to say that according to the rules of visibility in 5E, when something is blocked by something else, there is nothing anyone can do to see through it except for possess the above abilities. You are 'blinded' by the object that is blocking you, and until that thing that is blocking you is removed, you will always be 'blinded' by it.

Tremorsense and Blindsight are the two things that RAW let you detect the location of things without having to see them, and as such these are the two RAW things that would let you look through heavy smoke. Neither is available as a class ability, so your PCs are not likely to have access to them.

As you mention, Blindsense does not let you see through smoke, because Blindsense only works when the person you're looking for is hidden (took the hide action) or invisible (had invisibility cast on them).

Starting at 14th level, if you are able to hear, you are aware of the location of any hidden or invisible creature within 10 feet of you.

If you're just standing in a fog cloud, then someone with Blindsense cannot detect you any better than someone without Blindsense.

If you're worried about a smoky room, you can look at the spell Fog Cloud to see other ways to get around it, mainly:

[the fog cloud] lasts for the duration or until a wind of moderate or greater speed (at least 10 miles per hour) disperses it.

So, it looks like RAW, mild to moderate winds can disperse fog/smoke to a degree that it stops interfering with vision. In that case, if one of your PCs has a spell that generates wind, then by the Fog Cloud rules they could use it to disperse the smoke and see through it.

They could also have the party barbarian tie large paper fans to his arms and flap them like the dickens, but that may or may not be too silly for your campaign.

I spent about an hour looking, but I can no longer find the article, interview, video, or tweet I'm looking for. However, I'm certain that at some point there was a discussion with the designers about how much a given PC race's vision type counted for balance, and the response was basically, "none at all." In other words, the game designers did not rank PC darkvision as being significantly more valuable than normal vision for balance purposes, and treated it as a flavor component of each race.

I know a lot of players disagree, probably because every player seems to have a self-sufficiency reflex. And the Darkvision spell seems anomalous until you realize that it's 2nd level because it's specifically for when the narrow uses of darkvision exactly come into play. It's the same reason Knock and Spider Climb are 2nd level. They're not needed all that often, but when they are they're very useful.

Keep in mind that if you're following the game's rules that complete darkness is dim light to a character with darkvision, then characters with darkvision wandering around without a light source is only slightly less stupid than it is for characters with normal vision (-5 to passive Perception and disadvantage on Perception rolls). Such a party is all but guaranteed to trip every trap in the dungeon, and tasks like reading are likely going to be flat out impossible unless the print is particularly large. Even a party of Dwarves should be using a light source in an unfamiliar tunnel. Though light sources can be seen by other creatures, sound is often a bigger giveaway about the presence of other creatures.

Bottom line is that, from a design perspective, it's apparently not worth very much. At that level, I would grant an additional language, vehicle proficiency, or tool proficiency. Alternately, you might grant perception advantage in certain circumstances (e.g., Dwarves and Rock Gnomes underground, Elves and Forest Gnomes in the wilderness, etc.).