...'s not many problems you can confront a Starship with unless you resort to contriving some reason for the tech not to work every week. This is why Disco has limited the Spore drive to only being operable by Stamets and having it dangerous for him to use.
Giving them a properly functioning super warp drive so they can casually hop between quadrants and galaxies would mean there's no dangerous situation they couldn't just run away from. Giving an enemy an equivalent would also pose the difficult question as to why they haven't gone and attacked the Milky Way.
Also, while the mission of exploration is a useful way of explaining why the ship is out there, none of Trek's best outings have ever been about exploration. They usually involve some sort of military conflict, time travel, alternate realities, or even all of the above. You don't need to go hopping galaxies for that.
