Anything that is labeled in any way (but usually by a press-release or review in a major magazine) will ultimately become a "genre." Let's see ... it was "garage rock" then "college rock" then "alternative rock" then "grunge" and so on. Yes, stylistically you might suppose that those forms are different but it's the social movement that is basically the same; music evolves and THANK GOD.
Why does this happen? Well, the majors are always finding bands and recording them and then shelving them. Then when a sound gets some attention, they will go through their catalog and release anything that sounds remotely like the same. Or they will "create" bands that sound the same, or bands will form on their own that sound like the first one. You see. It's been going on for decades.
As far as "lazy vocals and mismatched instruments"; what do you mean? Compared to what? Compared to big-budget releases? Yeah ... that's because most singers do multiple takes of the song and then an engineer comps those takes into one good one. Usually using "very nice" microphones and other "very nice" things in the signal path. The vocals takes are processed even further (either pre or post take) with other "very nice" equipment (as opposed to "plugins"). Typical "independent" artists don't spend as much time or money on those vocals.
I'm not sure what you mean exactly by "mismatched instruments." Again, big-budget releases have access to many, many different pieces of equipment (amps, guitars, effects boxes, etc.). Independent artists are lucky to have one good amp and one good guitar.
And let's not even start talking about the "space" that music is recorded in.
Of course, NONE OF THE ABOVE is a requirement for a killer record or band. If you've got good material and decent performers you can set up one microphone in the middle of a decent sounding room and have a record that people will respond to positively. I just wanted to illustrate a point about the difference between why some records sound great but have crappy music and other records may sound "lazy" but have great music.
To me "indie" has become a genre that is not necessarily indicative of the bands signed status. You can have an indie sound while being signed to a major. I have no problem with that ... you can't fight it anyway. "They" will always try to find a way to market the next big thing.
Does indie mean you can't use a studio or engineer to record a release? Does it mean you can only use up to a certain class of studio? Does it mean you're obscure? Unsigned? If it just means that you merely maintain control of your music and publishing then there are a lot of indie bands out there on major labels.
What indie bands do I like? I guess I'll plug my own band here:
Chess Club. We recorded our first full-length in a major studio with a major engineer. We paid for it ourselves, we maintain control of our publishing and we're obscure and unsigned. I guess that makes us independent but our sound may not be "indie."