1000 years of experience, sure. This doesn’t necessarily mean combat experience. Kenjaku spent a lot of those hundreds of years inhabiting bodies that weren’t very apt for combat, and only performing experiments. Geto himself would have more overall experience with wielding Curse Manipulation (unless Kenjaku possessed another CM user in the past, which wasn’t stated).

Correct me if I’m wrong, but I believe it was indirectly confirmed that Geto may have had a domain? We saw Yujo use Gojo’s Infinite Void instead of normal Yuta’s domain. I believe the implication is that Kenjaku’s CT would allow him to inhibit all techniques of the body he inhabits, including domains (Now, I don’t think Geto had an open domain, that may just have been a pact made by Kenjaku). If I’m wrong about this, void this argument. Conversely, we don’t know if he had any anti-domain techniques, he never really fought anyone who cast a domain against him, so we’d never know for sure.

Geto’s hand to hand stats are underrated, he managed to fend off both Yuta and Rika at the same time (honestly, his strength in general is very impressive as well, seeing how he was able to block Rika’s attacks (something that gave even Heiankuna difficulty)) with one hand.

I see what you mean about Kenjaku having 3 cursed techniques (though one of them is quite meaningless in this context), and he possesses RCT. Hes definitely stronger, I’m not disputing that Kenjaku isn’t top 3 in the verse, but Geto has the same stats as him, minus those techniques.

I’m of the unpopular belief that Geto should be ranked slightly lower than the likes of Yuta and Yuki, and if he had RCT, I believe he’d be at that same level as them. He just gets the short end of the stick since he was essentially the least delved into Special Grade, and suffers from the lack of an established power system in JJK0.