Porn is on the pathetic side of the sin of Lust. It’s on the same scale of patheticness (that’s not a real word but it ought to be) as DIY Sex, for which it is custom-made for.
Is it really a big deal? No, it’s a small deal, and a stupid reason to Sin. And because God does not use a sliding scale for Sin, porn is a stupid reason to go to Hell for.
Since porn (lust/sin) is one of the gateways to Hell...it's a very big deal!