Having worked as a barista in the past, I can confidently say that the quality of your drink depends more on the management you don't see than the baristas you do see. At their utmost, baristas can take something from OK to great. However, a few simple areas of ignorance or indifference by management, such as not testing and controlling the water quality, using poor quality or poorly roasted coffee, or letting the grinder burrs fall out of shape, will have a far greater overall effect than the vast majority of baristas who are either good or bad at their jobs. I suppose a truly horrible barista who is trying their best to get grounds in your drink, extract poorly, and burn your milk might be able to exert more negative influence than management, but the reality is that most employees rise to at least the minimum expectation of management; and most cafe managers don't really know or care that much about coffee compared to a true coffee nerd . So it takes management to get your drink to be consistently anything. Above that baseline established by management, if your drink is really good it is probably attributable to the barista's passion, OCD, or just luck. I'm sure pay is a powerful factor, but I don't think it's the primary one. I'd say the training, example, motivation and information provided, raw materials provided, and minimum expectations set by management are the primary factors in most cases.
Sure, the best case scenario is to get a dedicated nerd like me who had read books and papers on espresso before ever working as a barista, who can't pull a bad shot even if I hate the customer's guts, because that would be a crime against coffee which is more important than some idiot who ordered a four shot latte when he's late for work and is now staring at me impatiently and checking his watch every four seconds; sure, you'll want to get a barista who actually thoroughly rinses every part of the portafilter and grouphead and distributes the shot before tamping, but let's be real: that is like a one in five hundred chance when it comes to actual baristas. Most of them are trying to be screen and/or comic book writers, remember? No, the best you can hope for and go looking for is good management that knows and cares about coffee.