England last won an Ashes Test in Australia in 2010/11 since when 0-13. After the 2021/22 series a review pointed to a quantity problem with domestic cricket: 
there’s too much of it. For every team sheet in Australia’s red-ball competition, the Sheffield Shield, there are four in the Championship, allow for the number of players, the weather and there is a noticeable difference in the playing days for individual players.
The Sheffield Shield is played almost entirely by Australians, arguably making it more focussed, intense with the influence of Test players, past and present, greater. Possibly, although when it comes to Test cricketers
the Championship with its openess scales up pretty well, and with these numbers also reasonable to ask why isn’t domestic cricket a sizeable advantage to England? Maybe it is of course, just not obviously given a legacy of spending big on buildings and not giving enough for the playing base.
When Joe Root tossed up at the Gabba in 2021 he was starting his 13th Test that year, Pat Cummins his third, and England’s players continue to play on more days because England continues to play more Tests; an average of 
75 days to the Australians 61 in 2024(/5). No doubting either how reliant England’s Test team has been on those who play the most, almost half the names on team sheets those who had a schedule of 100 days plus. A too much problem, but £, Sky, T20 leagues and market forces; or, actually okay, England’s best in demand and just doing what they should be doing?
Going from year to season the number of playing days for English players, averaging 75 and 39, is in proportion. 
Some variation between the counties certainly, different numbers of players, how much white-ball they play etc, but not a concentration of smaller counties near the top of the table. Plainly other Test nations put out competitive teams with fewer domestic players, but in England, starting from here, it’s not obvious that contraction below would result in an advance above.
Data compiled from Cricket Archive.