My credentials are, I've watched all 3 series of Startgate, way to many times. For more than a year, I had PlutoTV just set to the StarGate channel. I also own the Blu-rays, but PlutoTV is convenient. And of course I've seen the OG movie several times (less then the SG-1 movies). But we will not speak of Stargate Origins...

I know some of these things aren't new. Some might be (the internet is vast... after all).

So, one thing I want to address actually "fixes" two things. For the Ancients, Furlings, and Goa'uld, fixing aesthetics and lore.

tl;dr The Ancients should have had a common Gothic aesthetic. The Furlings should be written back in and used to explain various aspects of the Goa'uld, and the Goa'uld should be way more fearsome (in the reboot).

In the show, I always hated how the Ancients were depicted. And it wasn't until recently that I finally figured out why. Nothing with the Ancients is aesthetically coherent. The various stargates we see, the various tech lying about, both old and new... none of it really lines up nicely. But it should have. Earth is covered with evidence of various aliens throughout the ages. Beyond the Asgard, Ancients, and Goa'uld, we know the Ohne were on Earth during the time of Babylon. Much of Earth's history and culture is derived from the various "gods" that we find out were various alien races.

So, lets fix the Ancients. Based on some tech we see, most notably the rings and DHD, the 'Repository of knowledge', and honestly Destiny, we get some ideas. So, Earthlings created castles, the whole gothic look... And I think, the Ancients' overall aesthetic should be closer to the Warhammer 40k Imperium (not exactly, but along those lines). Far more gothic. Their architect is big, bold, and intimidating. And we know humans didn't come up with it. In the episode 'The Torment of Tantalus' where we learn of the 4 races, we see... a castle. We can assume it predates humans and other than Ernest and SG-1, no human has ever set foot there. And based on what we know about Asgard and the Nox... that design must either be Furling or Ancient. And my next bit will describe why it's not Furling. But how we've seen the Ancients and their tech many times was just wrong. I believe, if Stargate got rebooted, if they stuck with a "gothic" design, things would line up better. We see castles in other worlds, too, like when SG-1 is tracking down Merlin (as well as many other examples).

So, a little setup for the next part. We know the Goa'uld are largely just scavengers. They're like the Borg of Stargate (assimilating technology and whatnot). And that would have been more true early on. The Goa'uld had a sort of symbiotic relationship with the Unas. We know the Unas are not a highly intelligent species as even today, they're still fairly basic (as in, despite all the time they still aren't in space). In the few times we've seen their homeworld, we see no technology. It wouldn't make sense that a lake snake-like parasite would just be swimming around thinking "Oh, if I get one of those Unas, I'm going to build me a spaceship!". I feel the Goa'uld when from 0 to 100 real fast as they are a real threat that several species have dedicated massive efforts to fight.

So if we extend that with what we know culters and whatnot were influenced by various "gods", we were told we "never saw the furlings"... I believe originally the Omeyocan (the Giant Aliens with the crystal skull), were the Furlings, but scripts as they are, that got changed. And the two names can co-exists because, as know, it stands to reason the Ancients weren't always called that. We see in the episode 'Crystal Skull', it has a giant pyramid, but not of Goa'uld design. I'm implying that the whole pyramid design and a good amount of tech was of Furling design, and it was stolen by the Goa'uld. We see in the episode 'Paradise Lost', the control panel has various shapes, including a pyramid, and it's specifically called out to be Furling. And in both episodes, 'Crystal Skull' and 'Paradise Lost', we see tech that allows for teleportation unlike anything the Asgard or Ancients used.

We also know, the Goa'uld would rather eliminate anyone they can't control. So it's very possible the "Giant Aliens" were physically incompatible with them. Hard to say. We know the Omeyocans were at war and were losing to the Goa'uld. So I think the pyramid ships and a bunch of Goa'uld tech are just Furling tech. And the "we've never seen the Furlings" still holds true as the "Giant Aliens" that we see could be a hologram or a form they currently are, or can take for humans.

And lastly, the Goa'uld in SG-1 are not as threatening or powerful as they should be. For that many species to be at war with them, they should be a bigger threat. I think if they reboot it, they should come to find out that killing Ra was a fluke. That they caught him off guard because he didn't predict Earth's military to show up. So he didn't have his normal fleet/guard/etc. and his guard was dropped. The fact that we got a nuke on his ship and blew him to hell.... pure luck. We did what the other System Lords couldn't do.