as you know, I always love to say that was also the bloody ECB/the Home Office who changed the rules for visa eligibility that made it impossible for players to go to county cricket unless you were already an international player. I can't remember the date the rules changed, but I became aware of it when Ed Cowan was on a Jarrod Kimber podcast prior to his test debut so I reckon the rules changed in the late 2000s. I think they were having the exact same discussion about young batting talent, and Kimber mentioned county and Cowan pointed to the Home Office.
For those that don't know, the rules were, excluding guys with British/EU passports who could get into the country, you had to have played 1 test in the last two years, or 5 tests over the last 5 years, to be eligible to get a County deal. There was also a set of criteria for white ball cricket, I think 10 ODers/T20s over the last two years or something. So my mind crosses to guys like Nic Maddinson and Kurtis Patterson who are perhaps examples of guys who may have benefited from County cricket, but they didn't become eligible until after their test debuts, and their eligibility was for a limited time as they both played under 5 test matches (ofc, for K-Pat, covid was a bigger issue)
Those eligibility rules have changed because of the Hundred, albeit the "additional" route is if you play 20 T20s over two years in an ICC full member country. My gut feel is more of our young bowlers hit that marker compared to our batters, and if a young batter does hit that mark, the IPL's probably calling. and also, the length of the BBL season being reduced might mean our players struggle to hit that marker now
The criteria was again up for discussion earlier this year:
https://www.espncricinfo.com/story/ecb-county-cricket-overseas-player-visa-criteria-1431989