It's funny how the stuff you worry about with your first child is a much bigger list than your second, third, etc. For example, our first child was treated so differently than the subsequent siblings in that we went out of our way to "protect" the child from any perceived harm. Like we would ALWAYS wash our hands with warm soap and water before going near the child for many months before we didn't worry about it. We would go out of our way to use hand sanitizer if we didn't have a sink and hand soap nearby. I mean we WASHED them and we forced other people to before they handled our child. Now, we aren't as worried about germs because what we've notice from our 2nd child onwards is that being too cautious actually may prevent the child's immune system from developing the natural resistance to germs. It's like a vaccination. You introduce the virus in a small amount in order to give the body the opportunity to develop antibodies.
Safety gates were standard fare for all our children. That hasn't changed. All of our kids were cordoned off from no-no places. But what has changed are the areas that we deem "off-limits". The range of access has increased progressively with each child. Early on, we had a fenced off area, either a circle or square so other geometric shape in one room like a family or living room. With our youngest now, we've made it so the kid could roam then entire first floor of our house. I guess part of the reason is that we have more eyes and ears spread out to keep tabs on the child.
Stairs are another story. They were in the realm of dangers with our first 2 or 3. But now I have found we started encouraging our 1 year old to learn to climb up and down the stairs a few months ago as soon as the baby could crawl. They're going to have to learn sooner or later a. Might as well have them learn under your watchful eyes so that when the time comes they try to sneak off and climb them, you won't be as worried because they will have learn that skill, probably taken a couple small falls in the process, but can tackle that without issue now. As soon as the child hit the crawling phase we would allow the kid to climb the stairs...with supervision, of course. Yes, we'd block it if we felt that there wouldn't be enough people around to keep the child safe, but it wouldn't be such an off-limits area that they wouldn't be able to try climbing up until much later on in their development.
What about outlet covers and cabinet safely latches? Or those spinning doorknob covers? I think we stopped using those with our 3rd child. In our experience, training the child to understand boundaries without chains is more beneficial. It definitely helps that people are everywhere in our house. And I don't believe everyone can get away with not having those devices. It's just for us, we've been able to train our kids what is OK and no OK to touch. Our one year old knows not to touch or open certain things after several or many times of stern warnings.
I'm sure I can come up with many other examples of how our child proofing has changed throughout the years, but you get the idea.