Anyone who claims that you obtained bad gas should be prepared to save you at least a 1 quart sample.
“Bad gas” can and does happen on occasion but generally that diagnosis can be translated to “we don’t know so we’re throwing something out there”.
Without a gas sample you have no recourse and anyone who gives this diagnosis should have it backed up with at least a 1 quart sample.
However, you state the car would not move with the engine revving. This could point to a transmission fault (automatic) or a clutch issue (hydraulics on a manual, etc). The exception might be if the engine were running so poorly (as in barely) that it simply would not move the vehicle.
The part about struggling to run at first after the car has been sitting points in another direction. This could mean a loss of residual fuel pressure and most of the time that is due to a faulty check valve in the fuel pump. At rest, residual fuel pressure will be lost and on a restart the struggling is caused by air being burped out of the fuel lines. Once the air is purged everything is fine.
As an analogy think of a garden hose lying out in the sun on a hot day. Turn on the water and the hose may spit and sputter for a while before clearing itself up.