It's interesting that so many countries don't seem to struggle to offer free university education (partial list linked to below).
This isn't an either/or thing, imho. We don't need to dilute funding to other areas of education or the NHS to do it, it is (as with most elements of public spending) a political choice. I'd suggest that a better educated populace, and not just in STEM subjects, is better for the country as a whole. Additionally, the provision of that education in itself drives employment in all other sectors of the economy.
I know something that's often been assumed is that having a student loan won't impact a person's ability to get a mortgage. It absolutely will - net monthly income with appropriate deductions for student loans is a key decision in affordability calculations.
As a vague aside, if you study until you're 21, you've still got another 47 years of productive, tax-paying work ahead to look forward to. If you earn more money because you're better educated, you'll end up paying back the government in additional taxation anyway!
Some countries in Europe, such as Norway, Finland, and Germany, provide free or low-cost university education for all students.
www.investopedia.com