Mining? Herbalism? Skinning? Every square inch of the entire worlds landscape is covered in literally mountains of gold. You just have to take the time to stop and pick it up.
Farm during queues or if you only have a short time to play and only have enough time to run a single mythic or whatever, instead of running that mythic, use it as a farming session. Unless you buy wow tokens, you can’t dedicate 100% of your in-game time to gear acquisition. You still have to generate income to support your instanced groups, whether its because you want enchants, or consumables, or to be able to repair.
If you are running out of gold, its because you aren’t spending any time on your personal economy. Correct that and you’ll be fine.
On a side note, there is no raid or dungeon that generates more gold per hour than just farming herb and ore in current content. Nothing even comes close. The only reason to run old raids for gold is if you absolutely despise farming and love running old raids and area totally okay with making a fraction of what you would if you were doing something different.