They are no-where near that size ...
they only get larger from there. Largest on my machine right now is showing to take 20GB. Granted there are a lot of shared layers between images, so the amount of space on-disk is much less than 20GB. But if you don't have any of the layers already? You're looking at 20GB easy.
I just downloaded: https://hub.docker.com/_/microsoft-dotnet-framework
It was about 2.7 / 2.8 GB in size.
Total size on disk was 8.7GB but we are talking about download here.
I would say you should be moving to .Net 6 it's been several years now that .Net Core has been out so there is no excuse.
None of this is an excuse to get a 10Gbps internet connection to your house. I have a 500Mbps connection and with the corporate firewall my laptop gets 100-200Mbps connection and pulling those containers was like 10 minutes.
Edit: In case anyone thinks I'm lying:
https://devblogs.microsoft.com/dotnet/we-made-windows-server...
I've never seen docker images of that size that can't be shrunk with multistage, or docker shrink. I can see how someone could get to that size with just baking in all their models to the image itself but yuck.