I would try to explain why the current itemization in Diablo 4 lays the foundation for the perfect Seasonal experience everybody would enjoy.

The current item tier structure in Diablo 4 is this:

Normal (white) -> Magic (blue) -> Rare (yellow) -> Set (green) -> Legendary (orange) and Mythic (red)

The concern of many players is that such item tier structure makes rare items redundant for the end-game. If Diablo 4 adopts the D2 itemization the item tiers would allow magic and rare items for end-game builds. But is this really needed?

What makes interesting the legendary items are their special properties modifying our skills and gameplay in unique ways. If we remove completely the legendary items from the game encouraging the players to min/max only magic and rare gear, what would happen with the idea of a meta game shift when a new Season starts?

Think about this... Take a break and think about this... Then take a longer break and think about this some more...

That is right - the meta game shift won't be that impactful, because the special properties of the legendary items are missing.

A min/maxing done entirely with legendary items would receive the biggest impact from a meta game shift serving for highest possible skill cap.

The more we rely on legendary affixes the bigger the meta game shift with each new Season:

Magic & Rare only -> Magic, Rare, Legendary on the same item tier -> Legendary only

Why we need a meta game shift and what is this exactly?

Simply said, if using A, B and C skills with A', B' and C' items is optimal during Season S, it won't be optimal when next Season SS occurs.

An impactful meta game shift would guarantee the ABC combo is not optimal during Season SS meaning that the player would need to solve the itemization again. And again in SSS. And again... A fresh theorycrafting and itemization game with each new Season.

That sounds like a skilled aRPG game and would be best achieved with the current tiered itemization the developers have decided to use.

But what about the simplified Math?

Simplified Math doesn't take the min/maxing away. It has no relation to it. Item stats serving for complex Math calculations only force the players to use online tools to "solve" the game. Complex min/maxing could be done entirely with a simple Math. And the more simple is the Math, the more newcomer friendlier is the itemization. Instead of having hundreds of "damage" stats on the items requiring a PhD in Math to properly solve, we have "Attack".

And having one stat for damage doesn't mean we won't be able to min/max. The legendary D4 items special properties serving for unique gameplays guarantee we would experience a complex min/maxing game in Diablo 4. It just won't depend on complex Math. And there is no need to. Diablo 4 is an action-RPG, not a math-RPG.

So, we have the perfect itemization in Diablo 4?

Not quite. I am seeing potential pitfalls with the mythic items, which may turn to what sets are in D3 if not properly designed.

We would be able to wear only 1 mythic item in Diablo 4. That means the developers understand the great power behind mythics.

If mythic items are designed to force us equip specific combos of legendaries after we find them then this would be the D3 sets case. If mythic items are just legendaries with 4 special properties instead of 1 then everything would be okay as long as these 4 properties roll randomly and are not designed to force us into specific gear. I have no idea what their current design philosophy with mythic items is, but I hope they are aware of the situation where they might turn these into D3 sets.

Last, I am against ancient versions of sets, legendaries or whatever other items. I am against tiered versions of items in general since these are simply more raw stats. And this type of game should be left to those who grind paragon in D3 - just remove them the 20k paragon cap and let them grind stats for life in D3. But please, don't do it in D4 masked behind tiers of items.

Don't require from your players to grind simple stats when you have such an amazing possibilities for creating end-games for all groups of players.