Ok well just to start, I wasn't using the reference to part 1 to compare them, I'm using it to make a point that Kakashi (already an elite jonin) feared Orochimaru before he even knew most of what he was capable of, I'm fully aware that Kakashi in part 1 and 2 are vaaaastly different.
It's not that he didn't knew Orochimarus arsenal. It's that he felt Orochimaru was stronger than him eventhough he didn't saw his arsenal, it was his personal feeling, so it has nothing to do with knowing his full arsenal or not. Kakashi has already shown he was able to evaluate someone hiding power even if he didn't used it. He knew Itachi had a hiding power when he fought him the first time, that's why he said to Kurenai and Asuma "he didn't even started yet, he is stronger than that". He also knew Naruto had the potential to surpass Yondaime, and that was loonnnng before he even become that strong. Like also when he felt Pain was stronger without even fighting himself(it was a clone), without knowing his full arsenal eventhough he fought bravely later. So, like i've said, he felt that Orochimaru was still stronger at that time, knowing his arsenal or not. Orochimaru also doesn't know Kakashis full arsenal, but he still felt himself as superior
Kakashi and Orochimaru are both adults, they have an equal chance to improve over an equal amount of time.
What i'm saying is that Orochimaru already had his long way as a shinobi, had much more time to improve himself as a shinobi, much more experience also in battle. You can't say that the Orochimaru who fought Hanzo(probably around Kakashis age at that time) for example(along with Tsunade, Jiraya and others) was as strong as the current, and he wasn't that strong simply because he was too young at that moment, less abilities, less experience, etc
At that moment he still had a great time to improve himself and become a better shinobi, exactly like Kakashi right now. But when you reach a certain age, your body capacities become weaker, and it's exactly what must happen with Orochimaru. Why do you think he always changes body? It's for that reason
You can't say that at 60years old for example, you can still do everything you could do at 20years old. Now you're talking about the forbidden jutsus he wants to learn. It's true that with experiments, he can still manage to develop some jutsus, but that is the only thing he can improve again. His battle capabilities in the contrary(taijutsu especially) are definitely becoming weaker with the time, and that's the great difference with a young Shinobi like Kakashi. Not saying that Orochimaru can't improve himself, but they are far from having equal chances to improve. Orochimarus prime is almost at his end.
The only thing he can do now to improve himself is doing his experiments as usual to developp some new jutsus. And when we even know that Sarutobi sealed his arms, he couldn't even improve his jutsus anymore. That are some reasons why i think part2 Orochimaru is much more weaker than himself in part1
Orochimaru acctually has more rescources to gain superior jutsu with his knowledge of forbidden techs, don't claim that Kakashi improved more just because he has a name-brand powerup like MS to prove it, Orochimaru himself said that he would never stop until he aquires every jutsu known to man, unless you believe he has already done this, there is room for him to improve. yknow?
What you don't understand is that part1 Orochimaru was stronger than part2 Orochimaru. He lost all his jutsus against Sarutobi, so he is obviously weaker, even Suigetsu said that recently
Second, Orochimaru's weakness was always sharingan GENJUTSU. Always, when bested by Itachi or Sasuke it was always via genjutsu. kakashi posesses different MS powers and has never shown a sharingan genjutsu tech.
This part is wrong. Firstly because Kakashi has already shown sharingan genjutsus in more than one occasion. Secondly is that you're underestimating Kamui greatly, it's an instant warping jutsu. Don't know how Orochimaru escape that. It's as if you were saying that Orochimaru can escape if Obito begins to warp him. If he can't escape Obitos kamui, he can't escape Kakashis kamui which is even faster(said by Obito himself)