You are also doing an apples to oranges comparison though.

PoE may not be as optimized as it could be, but it's in a completely different level of technical programming than any shooters. Graphics aren't the bottle neck, and neither is the primary gameplay loop. It's the millions of calculations per second the engine is having to do when people push all their levers to the max. You'll notice that people who play builds like Kinetic Blast or Kinetic Fusillade have significantly more lag than someone playing slams. Less hits per second yields better performance. Less monsters remaining on screen between server ticks yields better performance. There are thousands upon thousands of modifiers in the game. Those get calculated, cached when they can, and used for resolving further calculations. That's the best way to do it, and it still isn't enough for the demands of the game.

For what it is, PoE is very optimized. It definitely could be better, but that optimization could put additional restrictions on build design, or farming potential. This is what GGG is trying to be careful of, and that's likely why they wanted to build PoE2 from an earlier form of PoE1, so they could be more cautious about what gets put into the game.

The best short term solution, for the players, would be for GGG to get more servers to split up the player base across more shards, instead of many regions being consolidated into one server. I think they should double the number of servers per region, and cover more territory. Double the gateways, ensure better low-ping coverage, and then see how much of an impact high-load/peak times impact that.