Quoted from Fifty:Why isn't there more uniqueness, imagination, and passion outside homebrews?
I'd argue there's plenty, Stern is the conservative core, they mostly cookie cutter their games, keep the line moving, and product pumping, but other companies aren't doing that.
WOZ, Hobbit, Dialed In, Alien, Total Nuclear Annihilation, just to name a few, aren't like other games. WOZ and Hobbit are a little polarizing layout wise, but they're different. And full of ideas, whether you like them or not. Dialed In is a game from a major company with an original theme! Much love to Mark, but his game is 'licensed' you gotta give JJP props for daring to do an original game.
Alien has been a stupid rollercoaster, but you have to admit the layout from Dennis and Dave is different. Wide body with four flippers, not exactly something being pumped out now.
TNA is a throwback game, but name me a classic solid state that actually plays like it. You can't, it hasn't been done before. Now that's a homebrew, but it's being built, so it's basically transcended that label now.
I feel like your question really is "why are Stern games so boring and similar feeling now?"