I trust Valve to be lazy and swim in their sea of profits rather than go searching for more.
They have thus far avoided serious levels of enshittification because they don’t seem motivated in maximising immediate profits and killing their golden goose.
The day they get replaced by a competitive non-monopoly is the day it becomes a race for the bottom, who can invent the most predatory way to drain profits from users? Nobody else will be able to compete, so they’ll all be copying each other on their way down.