It's hard to say but in the 80's it was more likely a seriously talented driver could break through without multi millions of backing than the current era.
Mind you it was still very difficult for UK drivers and it must be said, Germans because they did not have major automotive or commercial backing like the best French and Italian guys had.
The nearest equiv to Hamilton in the 80's was probably Herbert before Brands '88 but he still needed a lot of financial help.