Old firm are English premier level, not championship level

I am fed up with the logical fallacy where people talk about the old firm being the quality of the English second division. Loads of people claim Celtic and Rangers are not English premier level sides, simply because they play in a league where most of the other teams are not of that level.
In logic and rhetoric, a fallacy is a misconception resulting from incorrect reasoning in argumentation.
This logic of some football fans is based on two logical fallacies.
1 / The logic is that as most of the teams in the SPL are not English premier this means all the teams in the SPL are not English premier. Under that logic. Every team in the Spanish league is only as good and no worse than the team in mid table. You are defining how good the old firm are on the basis of how good the average team in the SPL is. It is as illogical as me deciding your level of intelligence or height, based on the average iq or height, of your town rather than your IQ or height.
This is called the
Fallacy of the undistributed middle
The whole reason Celtic and Rangers run away with the SPL each year. Is because although the SPL is made up of mostly sides of the quality of the English championship and league one Celtic and Rangers of English premier sides. If they were just the quality of league on and championship teams they would be in mid table of the SPL.

This is the biggest way to make it easy for people to understand this point is.
If Celtic and Rangers are just championship level sides why dot they run away with the SPL every year.? Do you not realize the entire reason Celtic and Rangers run away with league is because the league is made up of mostly sides of the level of league one and the