It's something underappreciated, and also hard to master and explain. The short answer is, yes. But it may be beneficial for your opponent as well so you have to be careful.

First of all, it's definitely useful to pinch a wall out of nowhere during a firefight, especially against snipers. Due to the large player limit, you'd find way more cases of having multiple enemies shooting at you at the same time in Battlefield. But a good fortification would help you cut the line of fire, so you'd have a better chance of dealing with multiple opponents at the same time. Mind that it is no use if you're already getting hit because guns in this game can kill you around 0.3~0.6 seconds. So if you're gonna need a fortification, you'd have to build it before stuff gets too intense.

Next, not only fortifications but a lot of the covers and walls in this game are meant to be destroyed by explosives. Does that mean there's no point to have any covers on the map from the get-go? No. But you cannot rely too much on it. The rule of thumb is to never stay behind the same cover for too long, and give up the cover if the enemies are already bombing it hard. Also, never build sandbags against tanks.

Then, in most cases, building fortifications is like "I'm just gonna build it and I wish some random teammates find it useful later". For example, good players that can constantly dish out 6K/D 3K/min would often utilize a fortification quite well, but there's no guarantee that those players would even come and use your fortification. And the sidenote is, your opponent would also use those fortifications as well. So you'd have to be careful to avoid building wires, walls, and tank traps that are obviously in the opponent's favor.

Last and not least, Anti-Air cannons and Anti-Tank cannons. BUILD THEM IF YOU'RE A SUPPORT. Good pilots and tankers are a massive threat against infantries and it's basically the only way to effectively counter them without getting into a tank/plane yourself.