Here the real problem is that there is a design in D3 that some very small group of items are very much needed for the strongest meta builds and that those builds way too strongly outperform their closest competitor. We see that in the weapons as well. Said in another way, D3 has way too many unusable weapons/items in reality and way too few that are truly usable due to its design and even less viable options within a build. (One might also suspect that due to the influence of time in seasons you are acquiring a set and locked into that level of the game way too fast, instead of growing into it over time and have time to progress in D3, you are to quickly and easily at your final build components even if can get better versions of the same items).
The best solution to that is not trying to create and maintain a meta in first place like original D2 and D1 were, yeah I know it sounds old fashioned. There was a reason though why those games were designed without a real endgame. (any meta will be soon know through guides nowadays anyway), but unfortunately we all know or suspect D4 will be also about a designed and maintained meta endgame. Well then the other solution is another hard one, but mainly for the devs and in some talks it does seem they may be trying to go there and in others I doubt it.
That is to have enough builds for every class that also play really different and still do perform within a few percentage points of each others and do not have too many overlapping items and where missing one or two top items still make the build function at at least 90% efficiency of peak performance (This will never really work with big numbers though) and where you can meaningful progress until you get to that point and maybe even more importantly some rock, paper, scissors where a barb most of time will beat a monk in efficiency, while loses to a wiz and wiz loses to a monk.
D3 weirdly enough did try some of this, but weapons and items as stat sticks did make it fail. All those level 70 items and even sets you can craft at Haedrig could have been potentially your first power level in game while progressing to stronger builds if too many of them were not utterly BS, while others OP …
If we look back at old RPG’s though (that is one of the fathers of ARPG) before online even existed they have been solving the problem already for years. Have NPC’s selling the items you need for strong builds, but not the strongest. Those are from special monsters and often guaranteed drops, now that last works a bit less in the slot machine that an ARPG is supposed to be. Still it can be used.
Have a design where tier 2 builds that can be made from buying/crafting, tier 1 from targetable drops and S-tier from RNG, just make sure that the S-tiers do not depend fully on having the exact correct 13 items to talk in D3 speak but at least 4-5 are interchangeable with others within 5% efficiency and that also gives different play styles so not everyone is locked into button mashing CD style. (Something the Blizz devs after North devs left went wrong when added OP runewords in D2 that were craftable and utterly predictable) It will give players a sense that they can keep progressing and growing even before they have the best items from RNG and those items you need to clear the game are available to get even if the best take a load of mat or gold or beating hard bosses first time even if that will take time. The super duper special items just make it easier or unlock more fun options or the top efficiency without per se needing 13 in the right combination as well.
Unfortunately that is way easier to do in an offline RPG that has a fixed gameplay since you do not have to redefine everything every time you want to change the meta (which with those kind of games only happens with an expansion), or if do not redefine go into a powercreep that makes balancing over whole game almost impossible and as we all know players hate nerves so powercreep will be a thing with regular meta changes unless devs put a lot of time in each change, maybe even more as just creating new story content would need which is expensive like hell.
Yeah I know many people say RPG’s give us many builds and freedom, but that is because they have way more tightly designed all those builds, item classes and your strength of build over the whole game. Another one of those paradoxes where tighter design gives greater freedom of choice in the end or at least the illusion also due to making sure a player never needs BiS to be great and loads and relative quick meta changes tend to eff up those designs.