Magic Circle has the following effect on creatures of a specified type:
The creature can't willingly enter the cylinder by nonmagical means. If the creature tries to use teleportation or interplanar travel to do so, it must first succeed on a Charisma saving throw.
Forcecage has a similar clause:
A creature inside the cage can’t leave it by nonmagical means. If the creature tries to use teleportation or interplanar travel to leave the cage, it must first make a Charisma saving throw.
On Does Otiluke's Resilient Sphere beat Magic Circle?, one insightful answer frame-challenged to suggest that any non-teleportation, non-interplanar-travel means of movement, so long as it were magical, could be used to enter a Magic Circle.
Is this correct? Could a creature unable to enter a Magic Circle use a non-teleportation spell, such as Levitate or Gaseous Form (which would then also allow escape from a cage-shape Forcecage), to move into it? This seems like it might go against the spirit of the spell, if all that is needed to escape is a bit of a magical "push".