So ads.. as much as I dislike the industry, that's also an eng intensive task, right, as you attempt to predict user tendencies, raise engagement by showing the right shit, capture more data, and engage in the bot arms race.
Both FB and Google have really successful systems for this, and it insulates them massively from brand safety concerns. It appears that Twitter never invested in this (which is kinda insane tbh), and hence the large brand advertisers have a lot more power over them.
The stated goal is exactly to get away from that...
Though, whatever approach you have in discovery, or ranking posts, you're having an impact on your users, and promote a certain dynamic, no? I imagine their next approach won't be the equivalent of letting go of the steering wheel, just maybe not mindlessly chasing the same metrics as they are currently.
Maybe that's a little too social psych to call tech/engineering, but I imagine the data science that would support that would be quite exciting.