Not even noticeable Beredras! And I don't necessarily think the ring saved middle earth, but I do believe its fate was set in stone when it was created. Its attempts at finding its master, IMO, doesn't necessarily mean it had a brain of its own, so to speak. It had a fate, just like the rest of Middle Earth according to Illuvatar's great symphony. It didn't want to destroy itself, it's just that it already had. So to speak. So in a way, it was the ring that saved the day as it brought itself to Gollum, then to Bilbo, then to Frodo, then back to Gollum, who was destined to die with it.
But I won't lie....this is just wild speculation lol. I think it's plausible, but technically nobody is wrong.
I do agree about your comment with the Valar though. In fact, they were actually known for NOT intervening in the affairs of Middle Earth. Pretty much the only ones who would occasionally do so were Orome way back in the day, as in when Men first appeared, and his faithful hound, as well as Ulmo and Osse, both Valar of water so they had easy access to anywhere. I wouldn't say Ulmo ever intervened to the extent that it could be classified as "having a hand in," mostly just broad advice, though Osse did. But he was kind of a jackass :p
In my opinion the only times you can say "the Valar" intervened are when they came to ME to trap Morgoth and send him to oblivion and sending the eagles to save Beren and Luthien/Sam and Frodo. And Maiar are more like....demigods. The children of the Valar moreso than Valar themselves. I am a little unsure what you mean by Radagast accidentally set up Gandalf? Once the four came to ME, they more or less dispersed. The only ones who REALLY kept in touch were Gandalf/Saruman. Radagast kept to himself as much as possible, maybe with the VERY occasional word from Gandalf. One thing I don't understand is how they didn't see Saruman becoming corrupt. Even before he left Valinor he reminded me so much of Melkor (Morgoth before he was Morgoth), in that he always played devil's advocate and just had a menacing tone about him.
Anyways, Smeagol, I think most people do give Gollum credit for destroying the ring moreso than Frodo. BUT Frodo gets credit for bringing it to Mount Doom though, which Gollum sure as hell would never have done. But again, the fate of the ring is just that. Fate. So perhaps it was Illuvatar that saved the day, though he (she??) technically ruined it too!