Reliability of new 2015 6.7 powerstroke or Cummins Diesel

According to TCM, for 2020 Ford has ‘quietly’ done yet another diesel redesign (block, heads, injection, etc) their 6.7 Diesel...Huh?? Seems that each generation is fairly short lived - why is this??...Dealer service depts must spend lots of time doing re-training...Nice trucks no doubt, but every since it was reported that they have to remove the cab to work on the engine, not really my cup of tea...