It doesn't mean you can't win a championship if you're training, it just means you have to pick and choose during the important weeks.
I've had seasons where I train all season long, but then have to stop training skills so I can train GS for the week leading up to the playoffs. If I didn't do that there was no way I could have won my playoff series.
The problem, to me, with taking away GS training, is that you leave too much up to chance in terms of what your GS will be. since even if you play optimal minutes, there is still a near 40% chance that your GS will drop, or not increase (if you're at 7 or 8).