And here I thought it was just a discussion with different points of view.
Surely you'd agree that someone, or most people anyway, setting up a new aquarium, are not going to have a separate tank to quarantine new fish. Even many experienced hobbyists roll the dice and add new fish to their established aquariums.
Some might even 'argue' that they just don't have the money or the space for another aquarium to dedicate for quarantine which is why I'm always quick to point out the clear bin or tote with a spare heater and a sponge filter that does the job with very little cost and the bin can later/normally be used to store 'stuff'... Like the emergency kit that contains battery operated air pump for power failures and other 'incidentals' we all end up collecting.