Unless you like sour :-)
Me personally I don’t like sour,
Acidity like you get in ripe grapes, peaches, plums, pink lady & gala apples, rose wine - I love it.
A little tart edge like cranberry, hibiscus tea, cox apples, sweetened lime/rhubarb/gooseberry, NZ Sauvignon Blanc…OK I can get with that, sometimes takes a bit of work.
Sour like unsweetened passion fruity/gooseberry/rhubarb, Pino Grigio. Not for me, but some do like it.
“Sourness” is, to me, more like harshly acidic (punishing), rather than “having acidity” (interesting, playful).
I struggle to see how sourness & bitterness can be confused. Proper hoppy, smoke like bitterness and astringency in espresso is possible but quite rare.
A drier pithy, ‘is this sour or bitter’ is most likely under-extraction, but ground too fine, si siltyness flattens off the sharpness, but vey unlikely to be over extraction.
If you can’t tell, maybe your shot is just to intense to unwrap, so brew to a longer ratio, as a little more dilution can make faults easier to perceive & separate.
Some acids are straight bitter, so acidity and sourness are not much more closely related than acidity & bitterness. Which is not helpful, but the corrective action is still the same - grind finer until things get better, then get worse, then back off to previous best. If nothing is good, pull to a longer ratio.