Am I a bad friend/rude for not engaging with my friends and giving one-word responses?

To answer your title? Yes. Aggressively so.

I don’t participate in their activities.

That's fine. There are plenty of friends I don't share the same activities with.

I don’t really ask them how they are, or what their interests are.

One of the core things about being a friend with someone is getting to know them. That means their emotional state and their general interests. If you don't show any interest in them, why would or should they show any interest in you? It's a wasted investment.

I don’t even engage in deep discussion with them unless I’m up for it.

I mean that's fine. It's everything else that's extremely problematic.

When my friend sends a video that reminded her of me or that she finds funny, I don’t click it and just ignore it.

Your friend reached out to say that they thought of you in a moment when they had no real reason to. They're saying that because they care and want to demonstrate that. By ignoring that, you are telling them that you don't care about whether or not they are interested in you. Whether you mean that is something else but that is the story you are telling them.

Maybe my friends are growing apart and they text me less because of this

Oh they 100% are. No one is going to stay in a one sided relationship for long because it's a waste of their effort. They care and be emotionally open but get nothing in return except pain. By you not engaging with them when they try to engage with you, that comes off as you having zero interest in them. They're going to start questioning why they keep talking to you when you don't talk back. They are going to eventually come to the conclusion that you are not demonstrating any interest in them because you just simply are not interested in them. They will stop talking to you entirely and any memories they've had of you will become tarnished in their mind as a one-sided friendship.

but I’m kind of okay with that because I know they will be there for me when I need it

You are making an insane gamble here that will not pay off. Why would they ever be there for you? You were never there for them. You didn't share in the small joys of life that they tried to share with you, why would they want to share in your miseries? They will only see you as a source of negative emotion. They will see you as sucking up their positive vibes towards you and showering them in negative emotion as they get nothing in return. Then they'll feel used as you only talk to them when you need something from them. They will see you using them for an emotional cushion and realize that the only thing they are to you is a crutch. When they make that realization, they will leave you and never look back.

and because I’m genuinely just tired/bored most of the time.

So are most people but we make time and effort for our friends.

One time, my friend asked me if I’d like to spend time with her, and I just point-blank said “No”.

I can guarantee you that you hurt the hell of their feelings. Whether or not they said it? They were pretty upset. They offered to spend time with you because they like you and wanted to share in that. Asked if you'd like to spend time with them for the same reason and you rejected it. They aren't going to know the reason unless you said it so they're just going to invent a reason. With all of your other behaviors? They're going to assume that you don't like them at all and stop trying.

IDK if that’s rude just because I’m being honest

No, you're being a dick. Being honest is telling the truth but that does not mean being aggressively blunt. That does not mean phrasing it in such a way as to hurt someone else or to be emotionally painful. You could have said no in a thousand different ways that would have been just as truthful while also not as hurtful.

and also because it’s not personal, I don’t want to engage with anyone.

Then you better not be surprised when no one wants to engage with you.