I know he's only actually opened the 1st gate before, but do you think he's trained enough to be able to open the 2nd/3rd gate? Maybe even the 4th/5th? If you think Kakashi can only open the 1st gate (which is completely valid, it's supposed to be subjective) then why do you think he can't do more? And if he is able to open more than 1, do you think he chooses not to because of his average-ish chakra pool/stamina? My personal opinion is he can reach the 4th/5th gate by the War Arc but it is extremely taxing on his body so it wouldn't have a long duration, it has too many downsides to it and his body is simply not suitable for the gates. Using something like the 5th gate would probably leave him bedridden for a good few weeks so it obviously wouldn't be a good idea, but the question in mind is whether or not he's capable. But at the end of the day, his vitality simply isn't strong enough for this type of stuff and he'd probably rather spend his chakra on wielding the Sharingan. If Rock Lee as a 12 year old Genin could open 5 gates, I'm thinking Kakashi maybe in his twenties (probably trains less often and less hardcore/less of a natural taijutsu fighter) could feasibly train to 3-5 gates, especially with Gai challenging him all the time.