It is certainly viable, in the sense of workable. It definitely works.
What it works for is where you match up your wishes what what the system does.
Each one of your alts/characters can have two professions. There are three gathering professions - all very safe choices in every expansion. Once, it was a safe bet and an interesting synergy to pick up the crafting profession for your own class, and its gathering equivalent, where relevant. You could make your own gear.
As a Priest, you could take Tailoring to make Cloth Armor. Tailoring has no necessary gathering profession, so you could take any gathering profession, or the other self-sufficient profession Enchanting.
This was the traditional view of professions.
However, as expansions went on, and everything but the current expansion faded in importance, a few things happened.
You now level FAR too quickly to skill up your profssions within any expansion below the latest. While you can still make cloth armor while levelling, it will be far too low-level for you by the time you learn to make it.
For the past couple of expansions, the devs have made the learning the expansions’ crafting skills quite time-consuming and convoluted. You can be very successful and make a LOT of gold at max level with crafting profs, but it takes a lot of focused effort.
So the general sense is: crafting professions are not good for goldmaking below the latest expansion, and then they are very good only if you apply yourself quite hard.
Double-gathering is very viable for gold, if you are in the world a lot.
If you want to know how to skill up a profession efficiently, or the best places to farm gathering materials, check out this site: https://www.wow-professions.com/profession-leveling-guides
Be careful what you ask for!
You are walking into a game full of people who collect things. Many would say that collecting things is the true end-game of WoW. Mounts, Pets, Toys, appearances …
The addon All The Things taunts me every time I log in. Right now, it tells me that I have collected 46,330 of the 66,983 things I could have collected on my mage.
That includes 3,618 of 5,723 Achievements. And the Achievements include things very very very easy, very very very hard, and outright weird.