Thanks for explaining. It’s great to get an insight into other people’s styles. You're right—our basic philosophies are on different planets! I've never even considered the idea of setting DCs based on which character is attempting the task. I wonder how many DMs operate that way?This is where our basic philosophy clashes. For lore I would call for an int check. It is ability scores that count in 5e. If they bring up arcana, history or what ever I might agree that arcana counts or history and ask if they are proficient. However, I would never gate information behind a DC 20 + or 30 check.
If they really cannot succeed then I would tell them you know nothing about it. if the Cliffs off Insanity really are impossible then I would tell them so. They would need specialist help or equipment.
I would not use the same dc either. The trained people might get a lower DC representing their greater chances of knowing something.
So to take your example: if the test is Arcana and the character is proficient and they make the Easy DC I would say that you don't know but you thing you may have seen some of those symbols relating to an ancient magical civilisation.
If they made the moderate DC then I would improve that and say that the symbols are Netherese. If they make the hard DC I would add more and more again if they make the impossible DC.
If they were not proficient I might make the information for each DC about a step or 2 steps harder.
If they have Legend Lore or some such I would give at least the Hard DC information and add where they might find out more. Or ask for a check and add in the impossible stuff as well.
I will not go around the table and let every one try. The may be able to help and give advantage or bardic inspiration or what ever,
Under the new mechanics I would reveal information on an autosuccess may be up to the Hard DC.
It seems to me that at that point you may as well dispense with stats entirely. And indeed, there are indie RPGs that do so—the players and the DM come to a mutual, qualitative understanding of the PCs’ strengths and weaknesses, and then the DM simply picks a success percentage that feels right for a given character for a given task.