The last league I bowled in was during the 1989-1990 season. It a big money scratch deal in South Florida in one of the former Don Cater alleys. Twenty-four, four-man teams. About two-thirds of us carried 200 or better (myself included).
The manager of it was John Weltzein, a former touring pro who once made an ABC Masters show and finished third. He had the highest average at 220. Bob Handley used to make cameo appearances as a sub. (His wife bowled in the league). There were also another dozen or so guys who shot regionals or a national stop or two. (They held what was once called Touring II status.)
There may have been about eight 300 games shot in that league. Sidepots? Well, it usually took a 260 or better. This was also during the ABC's short oil era.
Perhaps if anything a good bowler will always find a way to score regardless of era, lane conditions, or permissible bowling equipment being used. But it's my observation -- at least in 2017 -- a sport pattern is probably the only way to separate those with game or not.