Firefly bushes have 10 animation frames each lasting 3 ticks, equating to a 1.5 second blink cycle. Due to their emissive texture layers, the rapidity and regularity of this animation combined with the difference in overall brightness at nighttime is rather uncomfortable to look at, especially so for players like myself with sensory/cognitive processing difficulties.

I personally think the animation could be slowed down or mildened without necessarily compromising on visual appearance.

Steps to reproduce (possibly most extreme example)

1. Make a superflat world with the following preset: minecraft:grass_block,minecraft:firefly_bush;minecraft:plains;
2. Switch the time to midnight.
3. Look at the horizon or onto the world from high above.
4. Observe the degree to which the firefly bushes pulsate.

It's worth noting that the animation is not considered rapid enough to invoke seizures in those with photosensitive epilepsy by OFCOM regulations, but I would nonetheless appreciate some attention given to this.