The thing is there's a couple of things going against this argument.
1. Number 1 the assets increasing is a foregone conclusion, SE is updating the graphics so it's likely people who are currently lagging will have to drop out of the game or upgrade their systems. Unfortunate for some but true.
2. This game is a luxury good. Running this game with the base subscription for 1 year is $12.99 x12 = $154.00 annually, plus whatever the base game costs. A base PS5 costs $399.00. As such the cost to upgrade isn't unreasonable.
3. The cost to upgrade would be unreasonable if it happened often, however we can largely expect this game to run on the PS5 for half a decade or more. As it has for previous systems.
4. New games with more demanding graphics FFXIV will never have are selling just fine, meaning gamers at large are running systems more than capable already and do upgrade their systems occasionally.
5. Keeping the games graphics stale will prevent new gamers with their newer consoles and PCs from trying the game out on the basis that it is too outdated when they can play other RPGs with better graphics.
So while keeping the game stagnant may be a net plus for a minority of players. The majority of future gamers and current gamers will have systems more than capable of running the graphics update SE has underway. So this is merely showcasing some of the things I'd like to see as it happens.
Keeping a game locked to outdated specifications is a greater threat than keeping the game current, especially one that already costs $150 a year not including the base purchase or the expansions that will come out. None of this is implying the game needs a super computer to run well, but it should keep up with the generational increases in hardware capabilities.
And on the pure business sense of things, catering to players who can afford reasonable hardware is more profitable for SE as well because they will also likely indulge in further luxuries like mog station items and dyes since they enjoy having their characters look awesome.