Even if it is just Gen 1 Pokemon, it doesn't really matter. This is the anniversary of Gen 1. It isn't Gen 1 Pandering, it's celebrating.
If you want something other than Gen 1, well look no further than the main sets instead of complaining about a pack celebrating the first generation having first generation Pokemon.
It's celebrated "20 years of Pokemon". Gen 1 was only the first three years. This is meant to celebrate ALL of Pokemon, not just Gen 1.