The glass of the door can be replaced. It is even possible to "double up" the wood to increase the insulation value. The insulation value should not be a problem there, although the renovation of a wooden door by a carpenter also costs money, and the price difference to a new door then is not really there anymore.
For the locks, there are renovation locks, e.g. from Fuhr, which are very good. I have a motor lock from this manufacturer with a fingerprint scanner and opening via remote control. However, the carpenter has to mill the appropriate holes for this, which also costs money.
By the way, as a tip: cheap and technically absolutely good high-quality doors are most easily obtained as display models/stock doors. I recommend, for example, 1001Tür or Suedesign (that's where I got mine). But other manufacturers also have a "bargain bin" or "stock doors" section. They are then "only" standard sizes, but often also with side panels, and standard usually fits in new buildings.