Yes, really. Calls just go unanswered and you prioritise (and barely function!).
This sort of thing has been trialled. But normally the "telephone clerk" doesn't have the knowledge, experience or ability to deal with the problem at hand so just becomes a glorified message taker for the controller making the decision in the first place which puts you at square one.
Very true. Whilst the one person making the inbound call might have a legitimate and important query about the next depature from their station, or is a crew member working out if their train is running, there's could be a dozen people wanting the same information or have similar but differing queries/needs.
Information flows are very important. The controller making the decision isn't always the one actually broadcasting the decision expect to those immediately in the know (normally the driver, and signaller manager/supervisor / train running controller). They are reliant on that information being disemminated via various channels (CIS / secondary phone calls / messaging systems) which all trickle down. It is not something the railway has ever got brilliantly right and only gets harder as the service has intensified over decades. I think it's almost impossible to everything 100% correct, 100% of the time, especially when an incident is in its early stages.
Also nobody has a crystal ball. Doing A, B, C might seem best but give you a new issue at D which was hard to envisage an hour earlier. And sometimes there are sometimes where you only have one or two options given the immediate circumstances and it is known this will cause more problems down the line.
Depends what the situation is. Sometimes when all trains are at a stand on a significant portion or even all of a controller's route, you just have to wait it out. Sure you can consider plans and alterations (i.e shuttle services) but you don't necessary know when the lines will be reopened.
And this is overall a relatively minor incident for a controller to handle - a one-off, termination short of destination. People will endeavour to get things back as booked, but sometimes there are no options, and sometimes the situation unfolds mid-incident (e.g. checking with fleet a unit is available, it is fit for service, a driver can bring it off the depot / swap the unit, identify maintenance requirements end of day etc.) and things take time.
Overall, it would be great to have say double the amount of controllers, but if 90% of the time they are there not doing anything, people will start to question the cost of it all. Bad rail managers often see controllers sitting around chatting and go "Why are we paying all these people so much?!" whereas good rail managers go "ah, railway is running well for our passengers today then!".
It's definitely a hard job, and it is why the roles are generally some of the higher paid in most companies requiring a lot of different skillsets, experiences and knowledge. This is not to say there are not good and bad staff, like you'll see anywhere and one controller dealing with disruption might get a different result to another controller. I guarantee you that things are more complex than they seem - even those who work intensively within the railway don't have a full appreciation of it until they see a control room in full disruption!