I recently bought some Giro waterproof thermal shoe covers. Had high hopes of them working for colder winter temperatures this year.

Nope. They work great for when it's raining. But Friday morning it was about 38-39F and I used thick merino wool socks, my MTB shoes with thermal aerogel insoles (which I had to grind down the plastic "lugs" under the heel of the shoe to get the shoe covers to fit, and only just barely), and then the thermal covers. Nope. Toes still cold after 45 minutes and borderline numb after 75 minutes. And it wasn't even down to freezing yet.

Ridiculous. My stupid long@$$ toes I think. I guess the only thing that would work for me is those electric heated insoles. But those cost as much as some of those winter SPD boots.