It may be helpful to separate the radio network (which provides local coverage) from the core network (which provides switching, subscriber management & onward connectivity)
Short-duration local outages to individual sites or clusters of sites (the radio network) are part & parcel of an evolving network, and very much a BAU activity. Countrywide, dozens of sites will be offline at any given time for planned works - it's impossible to avoid, networks simply won't improve without them and the T&Cs allow for it.
Over time, without these short-duration single site outages, traffic growth would outstrip local capacity and congestion would become an issue - causing even more customer complaints.
The core network is a different beast, and outages here are very much more controlled due to the potential impact of them. When they are unavoidable, they're usually done overnight when traffic volumes are lower and thus the impact can be controlled. These are the network changes which the OP should be comparing with, rather than radio access ones.
