Well, if it's similar to RandomX they lose the ability to build ASICs for the task qnd GPU computation gives no meaningful advantage over a CPU.

It will force general computation hardware to be used instead of specialized hardware, which is a massive reduction in efficiency and increase in cost. If they need to replace hardware it will be more expensive.

It won't stop DDOS' but it will make it much more costly to operate with little to no change for anyone else.