I’ve found my finishing problem: I’m building things out of pine.
Traditional stain, gel stain, urethane, tung oil, danish oil…on oak, cherry or maple many of these look fine. No matter what I put on pine, it comes out looking like a septic prolapse.
Have you tried a wood conditioner / pre-stain?
For pine especially, it is typically recommended before applying any stains. Prevents the blotches you will tend to get otherwise.
Also, there’s a big difference between construction lumber and something like prime SYP/doug fir. One piece of advice I have seen is, if you want to build from construction pieces, avoid 2x4s. Buy 2x10s or 2x12s and rip the boards you need of out of them. Poor man’s quarter sawn.
I really only used a 2x4 because I was trying out my new milling tools and just wanted something cheap to play with, and I figured I could get some use out of what I made, so I replaced my keyboard tray. I now buy rough sawn lumber from a local sawyer.