Canada

Most guns nowadays use polymer frames and stocks. The term 'assault weapon' was first coined when most guns were still old fashion wooden stocks and didn't have many of the post-ww2 features such as protruding pistol grips and barrel shrouds/heat shields. Most guns in the 1970s and 80s that your average person had was probably a ww2 surplus rifle since there were tons of those around in the market.

But since then, and especially post -2000, most guns use more modern material and features. They aren't more powerful than old guns, but they do look different.

One thing that did change that no one talks about is ammunition. Modern ammo is much better and more consistent than older formulations, especially regarding primers and powders. But no one wants to make older corrosive and fouling mixtures that make maintenance annoying and reduce the useful life of the firearm.