Raugheahuesh64 From a passenger perspective, the purchased rail service to Gallarate was not provided as booked
You actually did not book a train. If you look at your ticket you will notice that there is no mention of a train on it. You will have been sold an Arcobaleno Transfrontaliere ticket, good for four hours of unlimited travel on all public transit in Ticino in the zones running from Bellinzona to the Italian border, and on the line to Malpensa from there. You could have even travelled by bus from within Bellinzona to the station with this ticket.
It is actually a common misconception. It is not because during purchase you picked a train from a schedule that your. ticket is actually a ticket only for that train.
And as long as it was possible to get to Malpensa the railways have delivered their part of the bargain.
It is up to the traveller to check the schedule when travel is imminent to see if there are no changes. And to plan travel to the airport not to tight.
Raugheahuesh64 Why was there no clear onboard announcement in English explaining that the train would terminate and require changing to a bus?
You were travelling to Amsterdam? I was there last week. In the trains from Schiphol to Amsterdam Central all announcements were in Dutch only, as were the displays in the train. That trains systems use the local language is to be expected. Anyway, did you not notice that everyone left in Varese? That would have been a signal to me.