I'm not sold that Kakashi has this lost. Kabuto has more and powerful weapons in his arsenal, no doubt at all. But I'd argue that Kakashi is smarter and a more nuanced shinobi; we witness Kabuto, while fighting Itachi and Sasuke, firing off his great weapons with little tactful thought.
Kakashi would have difficulty, yes, and I'm definitely not arguing that he would win, necessarily. But he is extremely skilled, possesses Kamui, has a nearly unmatched education in all ninja-craft, and has fought stronger opponents, after all... like when he battled the Tailed Beasts, and it could be argued that Obito as Kakashi fought him (MS Sharingan and Rinnegan) is stronger than Kabuto.
Well it also depends on the terrain. If it's the limestone cave environment, kakashi gets murked by inorganic reanimation after being blinded and and deafened by the white rage technique. And thats not even considering kabuto's hax healing , orochimaru substitution, and his techs from the sound 4. But if it's a more open terrain kakashi gets some more advantage, but not much.
I wouldn't say kabuto wasn't being tactical against itachi and sasuke, as one of them was an immortal with an arsenal that is a bad matchup for kabuto, and he wasnt trying to kill sasuke he was going for the cap ture so he was restricted, and yet he still did well such as catching them in genjustu. Kabuto is one of the smartest people in the series. Kakashi is probably just as intelligent, but it doesnt matter as kabuto outclasses him everywhere else, including stamima strength durability and speed. Kakashi vs obito is more of a matchup issue. Kakashi is the best person equipped to fight kamui because he has the other eye. And their fight happen ed in the kamui dimension and obito couldn't phase his body to the real world as he would be attacked. So obito lost his biggest advantage and kamui is the only reason he is OP. He also wasn't able to utilize the rinnegan, and he practically tied with kakashi. Kakashi is great but his bodily stats always let him down. So it was great to see him get perfect susanoo and a large power boost. If this was DMS kakashi, id have to give him the win in this fight.