Yes, you can. Of course you can learn Spanish as an adult. Unless… you can’t. Your ability to learn Spanish might be connected to your assumptions, to what you believe to be true about language learning.
Even though you probably know people who managed to learn Spanish in their ripe age, you might think your case is different. You say that you lack talent for languages, that your pronunciation sucks, and that it is already too late to get good at Spanish. Especially that: that you’re too late to the game.
‘I read an article online that tells it’s impossible to master foreign language pronunciation after you’re four years old,’ or ‘My teacher said that the only way to become fluent is to live in a Spanish speaking country for at least ten years.’ Excellent reasons to give up on any ambitions on getting good pronunciation or fluency in the language.
But, you know what? There’s also plenty of people —people not smarter than you, and even older than you— who learned Spanish to a high level despite starting in their 40’s, 50’s and beyond. They’ve always existed. It’s just that you choose to focus on those who are struggling, on those who ‘never learn’. You think so much about these people that end up identifying with them. You start seeing yourself as incapable of learning. No lo hagas.
Whenever you feel discouraged or have self-doubt on your abilities to learn Spanish, get inspiration from all the people who were able to reach their Spanish goals. They are just like you. And you can become one of them (if you decide that’s possible for you).