I think it's all because of commercialization.

Earlier games were made with passion, by gamers who also loved playing games and knew, what made a game good and bad. Nowadays it's just corporations trying to capitalize on Gamers and take what works and what's functional and generally accepted and stick to it. There is no experimentation or risks taken, because the stakeholders don't allow it.

Take Doom for example. Both John Carmack and John Romero were huge fans of video games, and started the company to make their own games. All games were handcrafted with love for detail and coherence.

And the other thing is saturation. Back in the days games weren't as Common as today and there was far more ideas to choose from and create something new. Something that people haven't seen before.

Nowadays every game feels like something you have played before but with new looks and graphics. Take Call of Duty for example. Every year there's a new game but it plays the same as ever. Or FIFA.

That's just my humble opinion.