Is having under 150psi in all cylinders a bad thing?

That depends upon three things:-

Which fuel type are you using? 150 PSI would be far too low for a diesel-powered engine.

Assuming yours is petrol/gas powered, how far below 150 PSI? It can drop a lot on higher mileage cars and still be fine as long as all cylinders have similar readings.

Whatever the readings are, did you get them cranking the engine with the throttle wide open? If not then repeat the test.

If they are all within 10% of each other it is probably good enough. Wear shows up as imbalance as well as declining numbers and the imbalance is more obvious.

depends on the vehicle and engine....you would need to look at the manufacturers specifications