Sebastian Bach was a pretty good composer; he presented a portfolio of unique works to the Margrave of Brandenburg to try to secure a position with him; they sat in a drawer unplayed; he could only get a job at a church where he had to teach unruly boys. He was largely unknown.
Wolfgang Mozart died in debt, his wife had to try to make money off his manuscripts, his body was thrown in a mass grave. He’d had to scrabble for anything he got.
By your standard, they were anything but first rate.
At the time they weren’t.
But tastes change over time and their works have acquired value since then.
I judge art by the “sofa rule”. If I wouldn’t pay for it to hang over my sofa, then it has no value.
Financial success (through sales to private entities) is the ONLY thing even close to an objective tool we have to measure an artist’s talent.
However, the tool is not foolproof. One exception is that there is not a (c)rap artist today that is any better than fourth rate. Face it, a Turret’s sufferer can do the same thing if you just set his vocal tic’s to a beat