Working full time is a proper job.
Under question is whether the individual is working for their own company, or for another. The issue with IR35 is that it requires their own company to pay tax as though all income were from another, without the individual being an employee of that other.
This does leave such individuals without the employment protections mandated by law, as their own company is - under IR35 - denied the income required to provide those protections.
Do you disagree that this is an issue?