I wasn't referring to the elite bowlers like Davidson and Trueman (who as I mentioned would probably be good across eras), but the average ones. A lot of bowlers back then were medium pace swing bowlers off short run-ups who we wouldn't see in international cricket since 80s onwards (and not because of selection bias).
You can take it for what it's worth, but I was looking for Fred Trueman articles when I encountered some guy's blog (who usually opined on political matters) talking about pace bowling over the the years, and the conviction that bowlers have gotten faster. He noted that Steven Finn was considered one of the fastest going around the county circuit (this was in 2012) and named
sixteen bowlers from the mid-late sixties county circuit who he thought from having watched them were at least as fast as Finn near his best. It's just one guys' word but since true medium pace (Shackleton, Cartwright) died out (thanks to the predominance of wicket covering) I think the improvement has been incremental at best, although I think some other countries took a longer time to catch up. And even then bowlers will tend to suit their environment, hence why ours are generally quicker than England's'.
One of the things the modern era has also shown that tiny swing > big swing when it comes to getting edges and wickets. Pace and bounce are really important and we've already seen many batsmen say how uncomfortable someone like Morne Morkel made them. Batting becoming more skillful, again, on average imo. You look at top order batsmen from even the Davidson era and those shots look amateurish to say the least. It might simultaneously be true that there has been an average decline in skill related to playing short balls because of helmets.
Trueman didn't just swing the ball miles at times but he bowled smaller out swingers, a great off cutter and could swing it back in too, although not always consistently. In any case the principle that the ball should only move 'just enough' has been around for a very long time, so there's nothing new there at all. Here's Charles Kortright in 1948, talking about players who played before WWI:
Richardson's long easy run, fine action, accuracy and speed, coupled with a little break-back from the off, made him a bowler to be feared; and another man I greatly admired was Walter Brearley, who took a much shorter run, but achieved real pace through a splendid body action. Such men as these could take seven or eight wickets in an innings on plumb pitches, nearly all clean bowled, because they bowled a length, bowled with their heads, and bowled at the stumps. What is the use of swerves if you beat the batsman, beat the wicket-keeper, and everybody else? Bowlers like Richardson used to move the ball just that vital inch or two off the pitch, and they hit the stumps.
Swing bowling also has a mental edge to it. with some batsmen tending to follow the ball and the line being much more deceptive. In Truman's case
here he is pitching the ball very far up to get Hunte to chase it to slip, which he does after first getting a four, and then the next ball to the new batsmen is much straighter and with less movement to try gain the edge more conventionally. You can have those sort of mind games when the ball moves a lot, especially if the bowler varies the movement. You can if it moves less too, but it's more attritional.
I don't see anything amateurish about the Davidson era batting. A lot of modern Australian batsmen have a hands well in front of the body position that Don Bradman pictures as an example of what
not to do. The fact that the Kookaburra doesn't swing much and that batsmen can now get forward all the time without fear of being hit has actually worsened techniques. Sure the modern era has plenty of wonderfully dextrous shots, but basic defence had been weakened to the point that teams will simply disintegrate when faced with the moving ball. I remember Charles Davis noting that no.6 batsmen average far less in collapse situations than they used to. You have guys like Nic Maddinson being chosen for their supposed attacking qualities, whereas you might have had someone defensive like Trevor Bailey come in at six in earlier times, who could arrest a collapse. The importance of pace and bounce is also so-so. Morkel may have made the batsmen uncomfortable but it's been Steyn, shorter and skiddy, and Philander, even shorter and gentle of pace by international standards, who have been getting the wickets. Tall, back of a length bowling is best on fairly bouncy roads (and no swing) i.e. Australia, where batsmen can freely push through the ball. On a soft English greentop you have to pitch the ball further up and play with softer hands much closer to the body. Bowled has declined as a dismissal because you can't force batsmen back as easily anymore. Wickets don't deteriorate as much so certain batting and bowling skills have been lost. Don't even get me started on wet or sticky pitches. Batting today is different, but while there are now more shots than ever I don't think there has been much improvement on the basics (defence), and maybe even a worsening in some places.
Edit: Um, am I turning into the new Richard? I hope not.