I currently have a job, but I'm hoping to find a better one. Trying to get senior software engineer roles at startups, and I'm getting lots of interviews, but even after making it to a few final rounds, it seems I'm not impressing them enough technically. I also don't really get any feedback, so I don't know what to improve. I leave each interview feeling like I satisfied them, but then not getting an offer. I'm not talking about l33tcode either. Either take home assignments or system design or just conversations.

Is there a company I can hire that would help me out with this that is worth the money? Willing to pay, but not willing to waste my money and time.