Short answer: the backing track isn't making you worse. It's making it audible.
Singing alone, there is no external reference at all. You tune each note against the previous one — and since you are the ruler, "in tune with me" and "in tune" feel identical.
Add a backing track and a harmonic reference shows up that doesn't negotiate. The drift that was always there becomes audible. Uncomfortable, but it's the information you needed.
While it stays a feeling, you can't correct it. What changes things is measuring: knowing whether you're flat, sharp or late, and on which notes specifically. A tuner showing the note in real time already helps. Better still is comparing against the song's original melody, note by note.
Measuring doesn't replace a teacher. Technique — support, breathing, register transitions — is lesson work. What measurement fixes is the blind spot: you can't hear in yourself what you hear in others.
Alone there is no external reference, so you tune to yourself and the drift never shows. A backing track brings a fixed harmonic reference that makes the drift audible. The music isn't making you worse, it's revealing.
By measuring instead of feeling. A pitch detector shows the note in real time; comparing against the song's original melody, note by note, also shows whether you're late as well as off pitch.
Yes. Too loud and you lose monitoring of your own voice and compensate by pushing, which usually drives the note sharp. Turning it down or using one earphone off helps.
StarSinger does those three steps for you. You upload a file you already have, it separates the vocals, transcribes the lyrics with per-syllable timing and gives you a karaoke that plays in the browser, with pitch scoring. Free right now.
The caveats, because they're real: the transcription gets words wrong on screamed or heavily distorted vocals, and processing takes well over the length of the song.
Try it free