This in itself is a fascinating concept. (pardon me as I take a tangeant, I swear I will answer your main point in another post!)
2e (and 1e?) had saving throws based on the level of the target. The competence of the caster or the power of the spell had no impact (although the type of spell could make a difference - save vs death, or save vs spells for example).
So under that paradigm, as a caster, at low levels almost all your save spells would hit , and a high level caster would see most of their save spells fail.
In 3e, it was much better, because the save odds were based on the level of the spell, the competence of the caster, and the level of the target. It meant however that low level save spells eventually became obsolete.
4e = ?
In 5e, save odds are based on the competence of the caster and level of the target, but not by the spell level.
This has the consequence that low level save spell do not become obsolete. A web spell still works fine in a high level fight.
What is the "best" system? I guess it depends on what outcome you prefer. I really do like the 5e "end state", but I readily admit it may not work the best for everyone.