If the risk was only one isolated blackout you might have a good point. I was quite aware of the August example you linked to. But still it seems the grid is somewhat vulnerable to such risks:
https://www.theguardian.com/busines...ear-misses-in-three-months-says-national-grid
Again the example you link to is ALL about frequency not capacity. We have plenty of capacity. There is a good argument to be made we don't have enough frequency response.
This is a strong argument for more Tesla batteries not more gas generators.
Not enough details in that article, but looks like a very localised incident which has nothing to do with capacity but a local fault exacerbated by a generator failing to start.As for the effect on a hospital (on another occasion):
https://www.gazettelive.co.uk/news/teesside-news/patients-james-cook-hospital-plunged-13946012
If you had a power cut in your house due to a workman drilling outside, then couldn't start your honda generator would that be the national grids fault, would it indicate they had a capacity issue?
I do note you didn't link the later article that states the generator did kick in.

James Cook bosses explain what happened in power cut at site
Patients were plunged into darkness on Thursday night, with reports of nurses using torches
“The hospital was powered by back-up generators until the mains power was restored and all critical service areas within the hospital had uninterrupted power supply at all times.
“All areas impacted by yesterday’s power cut are back to normal and we’d like to thank our estates team and Carillion who worked hard to ensure full power was restored as quickly and as safely as possible.”
The second line in this indicates it was a problem on the estate itself and nothing to do with the national grid at all. You should be questioning the hospital as to why they had this failure, and why wasn't more done?
Some trains, not all trains had this problem. Again not a national grid capacity issue but an engineering issue on those trains. A design flaw maybe or lack of training?And it also affects other infrastructure such as electric trains, which apparently don't restart when the power comes back on and engineers have to be sent out to fix them!
Keep plenty of candles and torches handy, or ... sit it out in your motorhome, where you can even have heating ... gosh, yet another good use!
So far you have not convinced me we need more power stations and that our generating capacity is low.