I struggle to come up with things that add value to a meeting - What do I say?

First, I recommend going through these other Taro career advice:

• "How can I be more active in meetings and earn the respect of senior engineers?"
• "It's hard processing what happens in meetings - How can I be more effective?"

I want to say something that's insightful and adds value to the conversation...

This is a common misconception I see among earlier-in-career engineers, and it's important that you get rid of it. This sets the bar too high for yourself, and this will lead to you never speaking up in meetings. The hard part is that talking in meetings and engaging is like any other skill: You get better at it over time, and the best way to learn it is just to start doing it.

A meeting tactic I didn't share in those other Q&A is that paraphrasing the content of the meeting can very effective. Here's how it works:

1. Some person in the meeting says a lot of stuff across several minutes.
2. You are having trouble grokking all of it, so you try to compress everything from #1 into a few core points mentally.
3. You say something like, "Let me say this back to you (and please correct me if I'm wrong): We can't use this external library as it's filled with security flaws and our security team can't patch them all in time because they're understaffed?"
4. If the person from #1 says yes, you now have a good understanding of what's going on and you probably helped clarify the situation for other people in the meeting who were struggling with full comprehension like you.
5. If you are wrong and get corrected, you will then have a correct understanding of what's going on and again, you clarified things for the rest of the team.

If you have a supportive team and you've gotten feedback that you should speak up more in meetings, I'm fairly confident your team will support you as you "break into" meetings more and start expressing yourself more often!

Alex already described Active Listening in his post, which is a very important skill to develop. Being able to succinctly restate key points helps your note taking, and allows these summarizations to occur that sort of “check point” what is being presented.

Beyond that, though, everyone will benefit from a “blotter” that goes out after a meeting, and using that as a jumping off point for further offline discussion. Some people cannot synthesize information, reflect on it, and have good feedback in a time-constrained situation. Everyone should have a voice, not just those that speak quickly in the meeting itself.

Assign a note taker who is not the presenter in every meeting, and have those notes sent to the team after, even if everyone wasn’t able to attend. Then you have an “in” to provide your thoughts in response there, and have a record of it.

Diversity makes us better, but that means having flexible channels for this kind of feedback. If the introverted people, or those that require longer reflection to give insightful feedback, or those with social anxiety are all dismissed because they can’t give a response in one’s of minutes in a meeting, that is a loss. Level the playing field, and it will yield benefits beyond your own ability to contribute.

Other answers have already provided excellent advice here. I am just adding my two cents here. You can add value to meetings not just by providing insights but also by asking good questions which can then help you and others get better understanding of the topic of discussion. Good questions can help uncover insights which were being overlooked before. Showing interest in the meeting is also participation. I'd recommend starting with a mindset of curiosity and letting your questions guide the way.

One thing I do, when I want to be sure to contribute to a meeting is to not try to come up with everything on the spot. You can adjust according to the conversation, but having a few bullet points ready before a meeting can get you past the dead air thinking time.

You also don't always need to be insightful. Other forms of contribution that I often wish to see more of is when ideas or options are presented, to give your opinion on which you prefer and why. This can support a teammate or avoid them going down a path that no one is aligned with but voices weren't raised.