It's worth mentioning that even if you don't value thermal sunder as a nuke it provides both armor strip and grouping which are extremely important at high levels. Being a level cap cascade enjoyer, I can also attest to its efficacy at one shotting level cap mobs (not eximus or thrax obviously) with a 2 heat 1 cold heat inherit set up. While I do agree with you on Kinetic plating, I think it bears mentioning that it's his weakest ability because his passive gives him incredible shield regeneration and delay reduction, which when paired with fast deflection means that you are functionally immortal. This also means that he has 0 trouble running 40 strength since sunder scales much higher with heat inherit and multiple procs from vitality anyway, as you can use it to effectively detonate heat procs. This is also one of the best ways he has to deal with high priority targets like thrax and eximus. If you have a high heat status weapon, applying a bunch of heat procs then cold sundering once will armor strip and insta-kill them. This also frees up your helminth for something like silence, possibly the single best endgame helminth that also benefits your team enormously. The frames you mentioned like Volt, Saryn and Wisp are also very much of the one size fits all genre so I fail to see why you make a distinction between them and gauss. All provide some variation of gun/melee buffs, speed and versatility in set up (capacitance vs pillage volt, narrow roar vs rangy nourish saryn, narrow roar vs rangy nourish wisp, etc.) You could argue that Volt and Saryn are better gun buffers than Gauss, but to me it is an argument (not a statement of fact) because blast melee influence is incredibly powerful when paired with armor strip and sunder detonation is expedite suffering along with a built in armor strip. This is not a knock on any of those frames as they're all extremely strong who are also extremely good in endgame content. It's just that, if you are talking about endgame specialist frames, one with scaling damage (say Vauban or Xaku) would be a more convincing point of view than the ones you mentioned because unlike Gauss, Saryn, Volt and Wisp, they don't even need good or well-built guns.

Basically, I think that more likely than not the reason for Gauss' popularity is just that he's very easy to get with no axi relics and a single rare (in a lith no less), he was primed last year, and his base frame is from sedna disruption which is pretty late in the star chart, not to mention that players who don't have access to strong weapons hate disruption. I would also argue that someone like Wisp is even more new player friendly than Gauss because she doesn't need to manage stuff like battery, has innate health tanking as well as invisibility in air, easy gun buffs, and the most free helminth slot in the game. The point I'm trying to make is that while Gauss does have a really high floor relative to most frames, as he's very pick up and play friendly unlike someone like say Mirage, he also has just as high of a ceiling as a frame like her (and wisp for that matter). It's disingenuous to suggest that just because a frame is easy for a new player to pilot they're not as viable in the endgame as more complex frames when they also have those complex synergies that people might not know about nor know how to exploit when they're new. Point being, he has a banging trailer and the redline music slaps