Since the idea was brought up by me, let me address your concerns with a bit more tact. Golurk has an otherwise unseen typing and excellent resistances and immunities, which naturally lead it to being able to deal with a variety of Pokemon well (to name some: Tauros, Zangoose, Arbok, Armaldo, Braviary, most other Ground-types, Gurdurr, Metang, Pinsir, Regirock, Sawk, most Poison-types... and these are just off the top of my head). Obviously, it doesn't do the job perfectly and you can't just slap it on any old team and watch it work wonders (if it did, it probably wouldn't be a set that we're testing right now!). It doesn't have to be threatening offensively. That's not the point of the set.
Not to mention that there are a lot of water, ice and grass types around, with a build like this, I'm afraid Golurk just simply won't be useful at all. It's pretty much as others have pointed out already: all that Golurk can do is already known, it's not like Golurk can really pull new sets out of nowhere with it's typing and stats.
While I did say the latter bit, it's not good practice to restrict yourself to only entertaining a few ideas, especially if the possibilities (like the ones I mentioned) are out there. You also need to understand that it's not like a physically defensive Golurk is going to be walling the entire metagame... proven sets like physically defensive Alomomola have trouble with Grass- and Water-types too. Why does it make Golurk any worse because it can't deal with certain threats in the metagame? I will agree, though, that RestTalk is pretty shitty recovery, and we can probably move away from it and work on the possibilities of other moves. I think that a lot of experimentation can be done with that ~set~ to figure out what to do with it. Something like DynamicPunch might be worth consideration, forcing switches and hitting most Normal-types for super effective damage (presumably with Spikes up, since this will likely be on a stallish/bulky team). Other plausible ideas include Toxic, Curse (for last mons, maybe? it'd beat Duosion which is a pain in the ass for stall teams), Iron Defense, Drain Punch for recovery (even if it's slight), or Safeguard, even. It's also got stuff like Protect for Leftovers recovery, which would probably work quite well with things like Wish from other Pokemon or Leech Seed, etc.
I imagine Golurk would work really well in combination with Alomomola and SDef Ludicolo (or maybe even Roselia), which together check basically every threat in the metagame barring something obnoxious like SubCM Gardevoir or Musharna in general (maybe it should just run that core with Skuntank?) as well as something like CB Torterra or Sawsbuck (Tangela or Vileplume is a possibility, too). You're trying too hard to compare it to existing Pokemon and their functions; this set by nature is very different from the likes of Lickilicky, Vileplume, and whatever else you mentioned.
I also didn't know that there's bad and good theorymon, either. Of course you don't expect the average opponent to be atrocious, but you don't expect Golurk to handle the whole metagame on its own, no?
