More often than not I feel these decisions are out of the developers hands.
As a dev, I want to use tree shaking to make my bundles small and optimize to make my website lighthouse score 100 across the board.
What happens? Marketing needs tag manager installed and then proceeds to async load 50 tracking scripts in the background.
Design wants the large hero images because on the high Res devices they use it looks slightly pixelated and when you push back, a quick screenshot to the PM will guarantee the ticket is added to the backlog.
Point being I'm not sure claiming that Devs hold the power is particularly constructive as there is a large portion on non-techies who have their own priorities to push.