Hello, it seems like there is a lot of byproducts (slag and tailings) coming from production lines. Can you consider some of the following options:
1. Make slag and tailings byproducts unaffected from productivity?
2. Reduce tailings from uranium processing (covarex enrichment outputs too much tailings in my opinion).

Productivity is intended as a way to make processing slag more efficient, gaining more useful resources as a result; researching it is obviously up to the player.
The main purpose of the mod is to introduce a challenge for players to overcome. Coping with slag and its products can sometimes be challenging.
However, you are correct regarding point 2. The amount of tailings produced was intended with a view to having my uranium changes mod installed; without that mod the amount of tailings makes less sense.
I will fix that in the next update.

Productivity is intended as a way to make processing slag more efficient, gaining more useful resources as a result; researching it is obviously up to the player.

I wanted to point that productivity is applied to slag and tailings as well as to intended product (a plate of metal). Slag processing productivity is different.