For a lot of these doors, repair still makes sense - a new spring, a fresh roller set, a logic board swap on the opener. Plenty of doors from a 1970s build just need a spring or a roller and they are good for another decade. But there is a point where patching stops being the right call, and we would rather name it than run up a bill.
If the door itself is a steel sectional from that same build era and the bottom panel has started to delaminate, or the track is bent past where it can be reset, you are not fixing a door, you are patching one. Welding a bent track back into true does not hold, and a door structurally compromised by a bad opener install or a hard car hit gets replaced, not patched.
Once a door from the 1960s or 70s era needs its second or third major repair, a full insulated steel or composite replacement almost always costs less over three years than keeping the old one alive one part at a time. We do not push replacement on every job, but we will not sell you a repair we already know is temporary.
If your door is original to a 1970s build and has never had the spring changed, that is often the first thing to fail - not because the door is bad, but because torsion springs are measured in cycles, and forty-plus years of daily use catches up.