based on my experience the generic 4.5″ bandsaw can be set up to cut pretty straight.
Forcing the blade will cause it to wander off the straight and narrow, so more haste, leess accuracy!
However to do this, it needs to be in good order, and carefully set up.
Already the need for bearings in good condition has mbeen mentioned, plus careful setting of the guide rollers. (They are on eccentric pins for adjustment. Once set, I have left mine alone!)
(Having the drive pulleys running true is a huge help!).
Setting the blade tension (I made a Jacques Maurel Tensionmeter) and setting the tracking carefully, with a new blade really improves matters.
Howard(WHY do I only spot the typos AFTER hitting Submit?)