Ight. So, I don't think I've spoken on Gholdengo yet, but after play several games of testing, I've formed an analysis that I would like to share. First, let's talk about the typing: Steel/Ghost. Together, as Steel/Ghost, Gholdengo already has, what I would consider, nigh defensive capabilities. I'm sure you all are aware that Steel happens to be one of the best defensive typings, and Ghost is, for the most part, neutral to everything. Thus, the overlapping between both types isn't really a hindrance at all.
Knowing this, let's look at individual typing. If you decide to Tera Type and get the ×2.0 STAB for either Steel or Ghost, your opponent is either faced with a problematic and overwhelming base stat Make It Rain or the already useful Shadow Ball that can score you easy SpD drops for a clean OHKO next attack. Gholdengo, also having impressive EVs, can take full advantage of a mechanic like Tera Type.
For Tera Type Gholdengo, I always think about the presence of Flutter Mane, and that prompts me to go for Fairy. Best part about going Fairy is that you can take full advantage of the generic ×1.5 STAB of Dazzling Gleam. Now, all of your, supposed, Dark and Ghost checks no longer exist, and you're neutral to your other weaknesses. This is just one of many Tera Types that Gholdengo can take complete use of.
Good as Gold is, quite literally, the icing on the cake. As many have mentioned before, Gholdengo is, "officially", our first anti-status mon. Taunt, Encore, and so on, so forth, are utterly useless when Gholdengo hits the field. Gholdengo can be used to dodge statuses the entire match, damn near invalidating their purpose at all unless you can position yourself right to take out Gholdengo. This isn't taking into consideration that the same said Gholdengo can Tera Type, and remove whatever you have from the field.
Did I mention that Gholdengo has recovery? That's right! The OG Recovery, too. Despite whatever PP Recovery has lost, 16 PP, if I'm not mistaken, is more than enough to keep Gholdengo around as a problem. You slap LO on Gholdengo, with a little bulk, and, now, you just win the Gholdengo mirrors. Anything else is getting brought into OHKO range (at the minimum). If y'all don't see that as problematic, I don't know what to tell you. Although, I know many of you would opt to use the suboptimal Air Balloon set.
Overall, using Gholdengo makes me feel like I will confidently win, most of the time, because I know I have two already great STAB moves, can take advantage of Tera Typing, can abuse certain items, unaffected by statuses, decent bulk, and efficient recovery. Yeah, can we PLEASE ban this thing for the sake of the SV OU community?
Edit: Inb4 you realize Gholdengo IS Flutter Mane 2.0.