There are very few cannon fodders nowadays. Every team is at least in tip-top shape even if they don't have very good individual quality. They have physical, strong players who could wear down the more technical sides. Case in point Iceland.
There's also footage of everything these good teams can do. From training, tactics, strengths, weaknesses, everything can be studied and planned to counter accordingly these days. Whereas in the past you had little footage and the weaker sides knew the basics, some players here and there and that was it.
It's an underrated aspect of why it's harder nowadays against the so called lower-level teams.