I'm not trying to convince you of anything, but if all of your soldering experience is from parts that came out of a 40 year-old arcade cabinet, don't beat yourself up: that is definitely what I would call soldering in hard mode. Depending on where it lived, everything in it is probably oxidized, corroded and covered in dust, cigarette tar, and possibly cooking oil. Even if you can't see/smell any of it, it's still there. Solder only works well on pristine, clean metals. Some metals are just simply marginal, and don't take solder well even if they were ostensibly designed for it. Flux helps, but can only do so much. The semi-good news is that you should stand a chance if you can clean the bejeezus out of whatever it is your soldering a LOT of alcohol and a stiff brush, and maybe some fine-grit sandpaper.

Will second this. When modding Xbox 360s, I used MrMario's guides and he would say repeatedly "clean, flux, tin", kinda stuck in my head. I did also tend to just clean the whole board while it was apart, but especially the point you're about to solder should be clean.

I have never used sandpaper on electronics, but I perhaps similarly use a fiberglass pen. Total game changer for getting old cartridge pins to read again for SNES and GBA games and such. Highly recommend picking one up.

A glass fiber pen is my go-to for cleaning groddy pads and pins and the like. Works a treat.