I also wonder if anything has shifted recently - I think Google Flights has been around for over a decade, and for most of that time it felt aligned with my interests - simplifying the process of finding the cheapest flights to get me where I want to go.
Unfortunately, it has recently seemed degraded in several ways.
1) It doesn't reliably offer round-trips made of 2 one-way tickets from 2 different airlines. 2) It doesn't reliably pick up new destinations. I recently saw an airline added a route that would allow me to reach a desired destination in 2 segments rather than 3. I excitedly searched for such itineraries and couldn't find them on Google Flights (but I could on the website for the airline, whose flights are generally on Google Flights). 3) I live in an area served by multiple airports. Similar to my first issue, I feel like Google Flights no longer reliably shows me round-trip itineraries that depart from one airport and arrive an another (e.g. depart from Heathrow, arrive back in London at Gatwick). Once I pick a departure airport it
Is it just me hitting some bugs or hiccups? Or is Google actively degrading Google Flights for some reason (too expensive?). Is Google trying to simplify things for naive users? Or is Google Flights abandonware within Google that is running without much ongoing support?