While Shastri didn't take any name, his obvious reference was Chennai Super Kings seamer Deepak Chahar, who has broken down at least thrice in match situations in the last eight months after being declared fit by Nitin Patel-headed Sports Science & Medical team at NCA.
Deepak Chahar's performance has declined significantly since his comeback. He has lost his pace and his line length discipline, and the only strengths he has left are early swing and variations in later stages. Unfortunately, he has become a poor bowler now, which is disappointing for his fans.
In 2019, Chahar was at his peak, and the Indian pace lineup with Bumrah, Shami, Deepak, and Bhuvi looked very dangerous. However, players have the highest responsibility for their own bodies, and they must understand their limits.
If a player feels discomfort but hides it to play matches, the NCA doctor might not be able to do much, even with normal scans and clearance. Players may hide injuries to play for big money, fame, or selection cases in IPL or international games.
Fitness should not be categorized as only one type, as each body is different. Azam Khan's physio warned that he might lose power with drastic weight loss. Mayank Agarwal lost some power, but public perception is that he got fitter. Weightlifting is not for everyone, as Viru pointed out.
Finally, acceptance is necessary, as not everyone can stay fit for a long time. This issue existed before, with Nehra, Shane Bond, and many others curtailing their careers due to injuries. Media accessibility should not blow everything out of proportion, nor should everyone be blamed for this reality.