Something I've never been that great at is spontaneous conversation. I'm more than capable of public speaking if I've prepared something in advance. But if someone asks me something out of the blue, I really struggle to engage in deep conversation. Afterwards I'll think to myself damn, why didn't I bring up X or Y?
Half the time I don't know what to add and I struggle to think of what to say. Sometimes words feel like they're on the tip of my tongue and I can't get them out, especially when I'm under pressure. And in group conversations, I find it hard to interject when I do think of a point. By the time a natural break comes along, the conversation has moved on.
I'd love to get better at this. What can I do to improve?
Bit of a left field suggestion but one thing that really helps is finding your people.
In my younger years I sometimes really struggled with casual conversation, I often felt like I was the weird guy who had nothing to say.
It turned out that was only really true when I was spending a lot of time with people with whom I had very little in common. As I got older I eventually found "my people". Friends who I click with, who I share values and interests with, who communicate similarly to me.
It's not about finding people who are just copies of you, that would be pretty boring and make for a real social echo chamber. You want a range of friends with different interests, from different walks of life. But you want them to be, for lack of a better term "compatible" with you.
If you happen to be neurodivergent then that adds a whooooole extra layer of complexity to conversational compatibility. There's a stereotype that autistic people are awkward or socially inept, which is complete rubbish. They just communicate differently to neurotypicals. Put a bunch of similar autistic people in a room together and watch them have no trouble at all making conversation with each other, in their own style.
Anyway, maybe this isn't relevant to you, and you're already happy with the people in your life. But it's worth taking the time to examine whether the reason you struggle to make conversation is because you're trying to make it with the wrong people.
I always had similar troubles as OP, and at the ripe age of 38 or so, I realized I have ADHD. But not the "loud can't sit still" version, I'm the "bored and sleepy" version, which nobody ever notices.
I have a much easier time talking to other people with similar symptoms. No offense, but to me, normal people just seem to say a lot of words without actually saying anything at all.
It can be hard. Honestly I got pretty lucky in that I was able to find lots of good people through work. There are good and bad parts to the industry I work in, I got hired by a company with a really strong culture that matched what I was looking for. So I was surrounded by a ton of people with similar values and overlapping interests.
Without that, I think mostly it's about trial and error. If you're struggling to find the right people, you need to be brave enough to keep putting yourself out there, and to walk away from groups that just aren't a good match. Like I said, not easy!