Is it using an SSD? Your graphics card is irrelevant. Most of your processor is irrelevant. If you use Windows 10 on a classic hard drive, you're going to have a bad time.
I believe someone mentions that feature updates like 1809/1803/etc are not actual patches based on current install, it is a complete OS reinstall, which explains the slow install.
See e.g. https://insider.windows.com/en-us/articles/were-listening-to...
However, the same comparison holds. I have an older backup PC in the basement with a hard drive, and it still takes just a few minutes to update in the background on Linux. Windows on that machine was simply unusable.
Single thread and cpu limited would explain it, since what I do have is almost unbeatable single-core performance from a high OC on an old i5.