They can be bad and that absolutely could happen, but I think steam is a rare example of a customer benefiting monopoly right now. Monopolies make the market less efficient and right now the most efficient market for computer games is enshitification galore, but valve is sitting in the way of that, manipulating the market and making games be less economically productive (by forcing them to be more pleasant for customers).

If we had 20 equally viable launchers/stores, it’d be a race to the bottom on price, which would force them all to enshittify or die