are you nuts??????

that older content gets easier is the intended way to do stuff

Instead, you should be asking for a "hard" version of said raids, with updated loot pools, level so you can use all current skillsets, dyable version of gear, new gear, and even maybe introduce more dynamic ilvl gear (so like, you get a lvl 50 piece that upgrades stats and ilvl aso you can use it up to lvl 79~80 or something) (and also ask for armor part pieces to go to their own currency tab and standarize it)

That would be a good time and resource investment, to give more content, updated boss fights, a retouch on dungeon visuals (even a palette swap would suffice imho so dont need to go over the top to remake them but as OP wants make fights challenging)