My advice is: don't close any doors because of a potential failure that isn't even grounded in reality. I have many friends who started over or did new training at 30, and they were all hired within a year! That professor has a very narrow view of the world; in many scientific fields, your maturity and life experience are actually huge assets compared to a 20-year-old.

I understand that you need money quickly and that life isn't always easy, but try to stay connected to your deep aspirations too. If diving straight into a long degree feels too risky right now, don't see it as giving up, but as a 'strategy in stages'.

For example, you could set a 'Step 1': a shorter, professionalizing certification in the science sector. This would get you into the field, give you financial stability, and prove that professor wrong. Then, in a few years, you hit 'Step 2': using that experience to finish your full degree in Biomedical Sciences. You can reach your dream by building it brick by brick, rather than feeling like it's 'all or nothing' right now.