All someone has to do to avoid being called a boomer is

Everyone born between 1945 and 1960 (in the US) is literally unable to do anything to avoid being known as and called a boomer. The word was around for decades before some stupid mean people tried to redefine it based on their ageism, or in other words their ridiculous belief that old people are evil.

isn’t a slur more than that?

Not really. I could provide actual specific examples, but I don't really want to start saying like, slurs, so. I think maybe if you think that you couldn't make a slur out of almost any word, then you're not being creative enough, or, you haven't acclimated to how creative some of these other guys can be.

Here, I'll come up with a theoretical example. You could probably make a slur out of, say, calling someone a banana-eater, right. I can even imagine two ways to do that.

You could have it be, okay, well, monkeys eat bananas, so, the banana eater is like a monkey, and then obviously comparing people to monkeys is gonna be a little bit of a red flag, is maybe racist, especially depending on whether or not you're using it to be racist, or applying it disproportionately to one group of people. I've seen people just throwing out, like, the specific lego number piece of the mass produced lego monkey, whenever they see a black guy online. I think, at that point, that's basically a slur, in how they're using it, and that's like, just a sequence of numbers.

Or, you could say, okay, well, bananas are kind of a phallic type of food, right, like hot dogs, or whatever, so, people eating bananas are gay, as a kind of substitute for a cock. So, it could also be a homophobic thing.

This is all dependent on the context of use, too. If you're exclusively calling one group "banana-eaters" based on their intrinsic traits, that's gonna turn that expression into a slur more. It could also be a statement of fact, right, oh, chuck over there, he's a banana-eater, he eats bananas, sure. It depends entirely on use. If you need evidence for how this shit can progress then you need only look at websites like 4chan or some other such nonsense.

On top of all this you kind of have the complications of, say, slurs only really applying to particular intrinsic traits that people have rather than others. Slurs can apply to black people, but calling someone a "cracker", despite being still based on an intrinsic trait, of white skin, isn't really a slur. Neither is, as upthread, calling someone a "boomer", because we all age over time, where it's sort of used generically just to refer to anyone older than you, or because it's usually applied as a reference to a very specific class of people that have a specific socioeconomic context, more than just being based on their age. You'll usually only hear people call, say, american boomers "boomers", in that context, but you won't hear that in, say, china, or africa, or most of south america, or whatever. It's a reference to the post-war boom years, explicitly.

There are also certain subcultures which re-appropriate slurs, which basically means that those words aren't really slurs in how they're being used in that subculture. I'm sure you can think of examples of that.