"I'm too old for this" is the single most common thing I hear from people who haven't started yet. Not from people who tried and struggled — from people who haven't tried at all. So let's actually look at what the research and the real examples say, instead of going with the gut feeling.
What the "critical period" myth gets wrong
There's a popular idea that language learning has a hard cutoff somewhere in childhood, after which your brain just can't do it the same way. That's a real phenomenon for achieving a completely accent-free, native-level pronunciation — but it has almost nothing to do with whether you can become genuinely conversational, confident, and understood. Those are two very different goals, and most adults conflate them.
A real example
One of my students started at 58, after retiring, with zero Spanish background — not even high school classes. He didn't have some special gift for languages. What he had was a very specific reason: grandchildren who spoke Spanish with their other grandparents, and he didn't want to sit outside every conversation at family dinners. Eight months in, he wasn't fluent, but he was following the table talk and jumping in with short sentences. That was the whole goal, and he hit it.
Adults don't learn slower than kids. They learn differently — and once you teach to that difference instead of fighting it, "too old" stops being a real obstacle.
The actual adult advantage
Kids learn through years of repetition and immersion they don't choose. Adults can shortcut a lot of that by understanding the logic behind a rule instead of just absorbing it slowly through exposure. You already know how grammar works, in general — you learned it once, in your first language. That's not nothing. That's a tool most children don't have yet.
So what's actually stopping people?
In my experience, it's rarely ability. It's usually one of two things: waiting for a "better time" that never quite arrives, or trying to learn in a way that doesn't fit how they actually think (heavy memorization, no real conversation, boring material). Fix either of those, and "too late" usually turns out to have been the wrong excuse the whole time.