In reality games became just a gateway to these slot machines or DLCs. i.e. development happened only in one direction: money.
There is no way to explain how 15 years ago developers were able to build incredible open worlds with hours of dialog and tons of possibilities worth 100s of hours of gameplay on a single pay model, except priorities change in the industry. Fast forward 15 years - all the progress and tools, developing practices, experience accumulated in the industry - but no real progress or innovations.
There are still games that push quality mark forward, but mass market is going away from it. Companies like EA have to make a choice: do we fund this game that will sell for 60$ and give 100s of hours of diverse gameplay or do we fund this online game with proven gameplay and sell ingame items for 1$/piece for next 2 years. Both of these games not only differ in terms of money they make, but also in terms of time people spend on them. So EA is better not to fund game 1 at all, to let people spend more limited gaming time on the game that has a potential for more profits.