Gondolas, like elevated monorails and trains, have an unfortunate failure mode which is 'stopped and trapped' so in the event the system has to stop, everyone is 'trapped'. Back in pre-historic times when Disney ran their 'people mover' (which finessed the load/unload option quite well with the moving platform, one load/unload every 10 seconds) they talked about systems with excess cable such that in an emergency the gondolas could all lower to the ground. But that is impractical in longer runs (the wire buffer needs to be too long) and has its own issue if it lowers the gondolas in a non-emergency situation.
The best things they have going for them are that you can easily re-use existing right of way, and the per-mile implementation costs can be lower than conventional light rail or subways.
My favorite system that was spec'd but never built was the Chicago PRT (Personal Rapid Transit) which had four person 'cars' on a track that worked like elevators. You pushed a button at the track and an empty car arrived, you got in and punched your destination. It didn't have to stop until you got there. That particular system had issues with the amount of computer power it needed, although today it would be trivial to implement. If you can imagine autonomous vehicles on a track with 'smart' switches, its a lot easier than a self driving car.