All pitches are flat now compared to then? Also, bowling is mostly poor....How do you get that? For most Test teams, a good portion of their bowling attack is good and overall their attacks are at least decent. Up to a few years ago the West Indies and Zimbabwe had decent bowling attacks as well.
Yes, up to a few years ago. But not since 2001/02. And this is the time that the likes of Ponting, Kallis, Dravid and Hussey are averaging 70+. There have been plenty of attacks in the last 7 years which have been composed of bowlers of whom none could be said to be Test-class. What a batsman of the calibre of Bradman, on flat pitches, would have done to these attacks does not bear thinking about.
I'd be very surprised if his performances wouldn't have been reduced a bit in the 1950s, 1970s, 1990s etc. when there was generally more in wickets for bowlers and better bowlers in general. But even so I can still see him averaging 80-90.
More cricket favours batsmen over bowlers true, but more cricket isn't a blessing for batsmen. They experience fatigue as well and more so with playing more games. They'll only be slightly better off than bowlers. Someone like Bradman would be batting a long time, thus more stress and fatigue.
One thing for sure - bowling at Bradman would make bowlers more fatigued than they normally are.
Thing to remember is that while far more international cricket is has been played in the last 10-20 years than ever before, cricket as a whole has not increased in volume. Bradman still batted about as regularly as does a batsman today, just at different levels.
Better bowlers is linked to the exploiting weaknesses. There are differences in laws and bowling styles and techniques now to then. As was mentioned before the inswinger and doosra weren't around then. Also, bowlers these days are fitter and thus bowl longer feeling less ill effects. They're more attacking too which leads to more runs but a better chance of getting wickets. Ignoring all that why are bowlers then better?
The inswinger most certainly was around in the 1930s and 1940s, as was the outswinger. And while the Doosra wasn't that was mainly because it didn't need to be. Mostly wickets allowed fingerspinners to turn the ball more in Bradman's day, so a good arm-ball sufficed. And on wickets where the standard fingerspinner's ball doesn't turn (which did still exist of course), nor does the Doosra, so neither are a great threat.
And what on Earth gives you the idea that bowlers bowl more these days? There may have been more unfit bowlers, but the best bowlers were every bit as fit then as now. They use more sophisticated methods these days, but that just means getting fit is easier.
There's no way to my mind that bowlers of the 1930s and 2001/02-current-day are significantly different. In both cases quality was fairly minimal.
Less variation now than before.....How do you know that? You were there in the 1930s to experience them? Ignoring that climatic conditions are changing it still doesn't make sense. India, Australia, England, the Caribbean, Pakistan, New Zealand, Bangladesh, Sri Lanka, Zimbabwe and South Africa are all similar according to your logic. Considering he only played in England and Australia I don't see how that wouldn't be a factor.
It's very well known that before covered wickets the amount of variety in a single country was massively greater than it is nowadays. And just because one wasn't around doesn't mean one can't compare - you can look at how a wicket played, read of what people talked about how a wicket played.
It's very likely there was more, not less, variance in wicket types in the 1930s than currently. As I say - there has never been a time when wickets have been more conformative to stereotype than the 2001/02-onwards period. Yes, sometimes you can indeed rock-up in South Africa and find a wicket near enough identical to one in England; likewise in New Zealand and Pakistan. Other things vary, but a flat pitch is a flat pitch, and there were a hell of a lot of them around 2001/02-2005/06 (been a few more spicy ones in the last couple of years but still far too many flatties).