This is simply not the case. It is a fundamental feature of every signaling system, and has been for over a century. Any collision would be caused by a seriously defective signalling system, not the stopped train.
Anyway, I'm sure you'll find a new reason to say why it's perfectly ok to stop trains with passengers in them willy nilly and how that isn't a safety issue but I'm just going to let it go here. I certainly hope you're not in charge of anything that involves public transport.
(Edit: you might be able to find some of these online, as regulators sometimes publish them for comment if there is a waiver request… not going to dox myself though)
Your point about external grade crossing hazards is valid… but also completely avoidable unless the train is super long (IE: not a passenger train) or the train was already going slow (like just leaving a station or signal).
There are separate system safety plans to ensure that timely/safe evacuation is possible regardless of where the train stops.
In the absolutely worst case, this means coupling another train and waiting the ~30 mins for people to walk through the train to the new cars, then uncoupling.
The most recent major incident is two months ago:
https://apnews.com/article/poland-train-accident-1db1a088c31...
And there are plenty of others to choose from:
https://en.wikipedia.org/wiki/Category:Railway_accidents_and...
There are only two countries in the EU that have worse rail infra than Poland (Romania, Bulgaria). Rolling stock is off mixed quality and vintage, maintenance spotty at best.