I don't really get why people find things like this so funny. Yes, warning systems have improved in recent years/decades as there wasn't previously the mechanism/awareness to provide such warnings. Things have changed.
But if you look what an amber health warning actually means, it's that the NHS might be affected and there may be travel disruption etc. For anyone that's ever worked in the NHS or had to travel during hot weather, I doubt that's wildly surprising.
If by issuing a warning prompts a few people to take sensible precautions such as staying out of the midday sun, wearing suncream, keeping hydrated, looking after elderly neighbours/relatives or making sensible travel plans, I don't really see what the issue is. I can guarantee there'll be an increase in morons complaining they've got entirely avoidable heatstroke over the weekend or other vulnerable people struggling.
Despite what people on football forums might laugh about, the climate is getting warmer (yeah, yeah it was hot in '76, I know) so gearing up for adapting to it can only be a good thing.
How the hell did I ever cope in the olden days?