The old school whistling fireworks were often based on picrate chemistry. Picrates famously have the ability when burned to hover between normally deflagration and true detonation; the whistling is a side effect of this. One of the largest non-nuclear explosions in history (see below) was a picrate explosion. These aren’t used anymore for safety reasons; they don’t have a great stability profile and picrates are true high-explosives.

Over the years they have found alternatives for and phased out most high-explosives used in fireworks. Many high-explosives will just deflagrate/burn but can spontaneously detonate with considerable power if the conditions are right, which makes them dangerous.

https://en.wikipedia.org/wiki/Halifax_Explosion

Have advances in explosives, fuses and quality control made fireworks safer in the last 40 years?

Or perhaps the safety improvements are offset by sellers now offering bigger fireworks (either because those are now actually safe and both buyers and sellers are more comfortable with them, or just because of a general hedonic improvement).

Or perhaps they are safer for their users, but worse for starting fires or interfering with low-flying aircraft.

Either way I would be interested in reading more about this, something more nuanced than "fireworks dangerous". At the least it's a counterpoint to what happened with illegal drugs which seem to have become more dangerous as a result of regulation and bans.