The flaw here is that the transporter recreates people in the same state they were in when they were destroyed to be tp’d, ensuring the cause for original degradation remains present and thus gaining continues

Unless, of course, the plot demands different. Notably in these episodes:

• Unnatural Selection: Dr. Pulaski ages rapidly and they use the transporter to repair her DNA and revert her to her normal age
• The Most Toys: O’Brien deactivates a weapon that Data fires just as he is being transported
• Realm of Fear: Barclay discovers a whole missing crew within the transporter beam somehow

And of course the bio filters that explain why nobody gets any unexpected diseases when they visit planets.