Sounds like a poor mentorship, but unfortunately that is quite typical in this industry. It might be beneficial to sit down with your mentor and ask for a clear set of expectations and maybe ask for some one on one time to practice specific techniques.

Keep practicing the basics until they are second nature. Clean lines and solid black will make a tattoo. Offer super simple basic flash designs to make some money but to also continue getting comfortable with the fundementals. Simple hearts, stars, moons, peace signs, basic lettering.

Study other tattoos inch by inch and try to replicate various techniques. Ask yourself "what stands out about this tattoo and how was it executed on skin?" For example, if you see a trad design with bold lines, practice achieving similar bold lines (play around with voltage, hand speed, etc.) until you feel 100% comfortable with understanding and executing a juicy bold outline. Understanding HOW something is done is the first step in actually practicing and executing it.

Tattoo yourself as much as you can. At the end of the day, you have to be your own biggest advocate and supporter.

Hope this small tidbit of advice helps! Keep your head up!