Thanks again for the video. It solved my problem.
If anyone bumps into this thread in the future, the static route showed in a screenshot above here was correct, however here's what I did wrong:
On site2 I had set "IPv4 Upstream gateway" in the interface config to the gateway on site1. This makes pfsense NAT the traffic instead of routing it. Here's a timestamped link to the video where this is explained.