Allowing more open development is fantastic. However, the summary (and really a ton of people) have the relationship at play with games backwards:
"This has helped developers focus less on creating a video game's underlying technology and more on the artistic and creative processes that actually make games fun to play."
The underlying technology, however, is the essence of the game. It's what tells us how mario moves compared to sonic or y metroid cant crawl. The artistic and creative process, while quite important, largely affect how a game is presented visually and thematically. The rise of one-size-fits-all platforms, designed to be broadly used not only between titles but between genres and platforms, has led to a massive homogenization of gameplay. Gameplay, of course, is what makes a game fun to actually play. Setting is not gameplay. Writing is not gameplay, and graphics aren't gameplay.
Yes, these platforms are customizable, but the distinctness that came with each game or class of games has largely been lost as games increasingly rely on generalized engines. Unity and Unreal (and various other engines) are great, but they're not responsible for freeing developers to make experimental games. To the extent that is happening, it is despite of, not because of, those engines.