Obviously not with Gmail/Facebook, in that case it's just 100% incentive misalignment.

The others, probably, VCs are incentivized to fund the people who allocate the most resources towards growth and marketing, as long as the app isn't actively on fire investors will actively push you away from allocating resources to make your tech good.

You would be surprised at how bad the “engineering culture” is at meta. There are surely people who care about page load latency but they are a tiny minority.