well, for your unfun level 20 dungeons...

open duty funder (U)
click on the gear in the top left
select Limited Leveling Roulette if you are the leader

the roulette chosen should be within 8 levels of the lowest team member

yes, not having your full kit at 80 is inconvenient, but have to remember, the game is also not entirely about you and what you want.
wandering Statasha with your full kit is fun... maybe once, and certainly is no challenge
but if you are doing a leveling at 79, chances are you are doing it for the rewards not much else. the xp rewards are boosted for those of a higher level so... its a trade off.