Is receiving privacy on Lightning still non-existent or has that been fixed somehow? I know you have good sending privacy on lightning but invoices reveal the receiving node to the sender and to all relaying nodes, right?

Yes, there is always so much more for me to learn. 

How can you mix an infinite amount of sats through a 1 million Sat channel?

Because now we have LN and is much better.
Just think about this simple fact: through a single 1M sats channel I can coinjoin/ mix/ /whirlpool/whatever you want to call it... infinite amount of sats without any onchain trace.

If you do not realize how powerful is this, you still have a lot to learn about LN.

Coinjoin onchain is a matter of the past, from the pre-LN era...