Losing photo quality when I export a raw photo as a jpeg in Lightroom Classic.

You may want to examine this in terms of JPEG quality settings:

http://regex.info/blog/lightroom-goodies/jpeg-quality/full-res-examples

Post a screenshot of your export settings. You might be scaling down the image considerably.

In addition to what @D Fosse said, you said:

I shouldn't lose quality I set the quality slider to 100%.

Simply not true, there is always compression and some loss of quality when you export a JPG, and so there is quality loss even when the quality slider is at 100 (also note that the quality slider is not percent, the quality slider is simply a number between 0 and 100)

You need to view at 100% to compare.

100% is a very significant number. It means one image pixel is represented by exactly one physical screen pixel. It's the only way to see the image pixel structure accurately (not resampled/softened).