The ATC / weather issue has nothing to do with BA. It is the standard operating procedure of commercial air carriers worldwide, especially in congested airspace such as Europe.

While it would be ideal to leave passengers in the lounge and then board only when the aircraft is ready to depart (as in wheels up), that simply is impossible. A change in wind direction or velocity, a minor technical fault on another aircraft, a bag to be removed on some other flight and so on and that opens slots for aircraft ready to fly. That may turn a 1-hour delay into 5 minutes.

This is not to suggest that there are not occasions when delays are inevitable and aircraft and thus passengers are held at the gate (lounge). But, this has nothing to do with BA and this really doesn't belong in a BA thread.

As to the tech issue on departure from GIG, unless OP can be more forthcoming about the nature of the problem and when it was discovered, it is hard to suggest that it is a "chronic" BA problem. Technical issues are discovered at all points in operations and dealt with when located. The Captain makes an informed decision as to how long the repair will take and that informs many things, including the return to the gate vs. sit on the ramp (I'm presuming that OP is mistaken as to his assertion that the aircraft sat on a "runway" for three hours at a station as large as GIG, but I was not there - however, this assertion leads to a concern that all the facts haven't been provided).

The chronic problem of crowded air space and bad weather has one solution. That is fewer flights. Not a solution which I prefer. I'll take the occasional ground hold as a "chronic" issue to be faced by all, not just BA.