Jackson67 said "Clear Lake is not a Provincial Park... "
The park is technically still open, as it's a national park, but there's basically no services available.
You are not forbidden from using "front and back country areas and green spaces", but there no washrooms, visitor services, and you are "responsible for your own safety", which I would interpret as they're not coming to rescue you if you get into trouble.
https://www.pc.gc.ca/en/voyage-travel/securite-safety/covid-19-info