Standard of cricket has gone down overall. Bangladesh haven't played very many good teams in order to improve.
West Indies - we all know they are just surviving as a cricketing nation due to past legacy. In a decade even that will be extinguished
South Africa - Nowhere close to what the immediate post-apartheid team was. Never will be.
Australia - Once a match against Australia was a guaranteed defeat and teams used to count their chances against other teams in the tournament. No more.
Pakistan - hasn't played much international cricket lately. A pity.
Sri Lanka - Could never repeat the magic from Jayasuriya / Aravinda D'Silva days.
That leaves only India, England and NZ among regular teams. You can't hone your skills playing infrequently against only 3 sides.
On the other hand soccer is fiercely competitive, that is why we see tiny countries like Croatia, Wales, Senegal etc getting better. League cricket is also important. If there was cross pollination between IPL, PSL, England County cricket etc, then players from smaller countries would get a better chance. For example, I would love to see Indian batsmen playing in PSL, Pakistani bowlers in IPL and more BD/SL players in both