I think you’re taking it a bit far, but I definitely agree that a paragon system like D3 can have value.
The core issue is the infinite, linear mainstat scaling and that its normal to basically max everything out within every season.
A couple of suggestions for a better system, that is still infinite:
You can dramatically increase the number of affixes in the paragon pool, take out the attack/defense stats. Set a mathematical limit that is appropriate for each affix - as you put points in, you get less and less and never more than the limit, but you can put an infinite number if you wish. When your DR gets too eggregious you move on to another stat you like.
You could optionally keep the idea of rotating points into categories/groups of paragon affixes, or just allow folks to put points into what they want.
In this way, you can combine an infinite system with finite ranges to control power growth.
The next component is to not power creep the power of items like in D3, where sets do 70k% more damage. The power creep in the gear we wear is a massive part of what enabled paragon to get so out of hand, because higher and higher GR became speed runs for XP every season, and higher and higher amounts of Paragon became obtainable within a season. This doesn’t need to happen in Diablo 4, even if they increase the raw level cap with expansions.
I think we should get far fewer raw paragon levels per season. It shouldn’t be possible to max everything out, and different builds would want different paragon configurations.
Say the level cap is 40. Perhaps the average player should have 40-50 paragon levels at seasons end, and high end players between 75-100. A paragon affix could take perhaps 10 paragon levels before it hits heavy DR and you want to move off into something else.
Thats all tuning, but essentially have more choices to make, make it so each affix has a set limit you can never hit (DR + Mathematical Limit), highly improbable to get all affixes into heavy DR range, and far fewer paragon levels attainable in a season. No attack/defense as options.