Why does a full validator node on eth2.0 does not need to be as powerful as a full node on eth1.0 ?

I have been reading that you can run a full validator node even on a raspberry pi. Can someone explain how this would work ? If the beacon chain selects a low power validator node for verifying a transaction, wouldn't this node take a long time to create a block? (and thus becoming a blocker)

Clearly, there are some holes in my understanding, looking for the helpful people of this subreddit to help me understand.

Thanks! 🙂