I can focus my eyes without glasses (20/15), and with glasses too. I can try on the glasses of a myopic person and still bring everything into focus, although it's an eye strain like I'm trying to focus on something 2 inches from my face. Astigmatism is tough though- either the horizontal is in focus, or the vertical, but not both at the same time.
One aspect of this that I haven't heard anyone talk about is the fact that you can get your eyes to focus more precisely if you practice. You can make out really fine details in something if you have bright enough light and you concentrate on one specific point and try really hard to make it as sharp as possible. You can focus on one ridge of the fingerprints on your hand and then look at the little imperfections on those. Or the individual fibers in a sweater. Likewise you can defocus your eyes just by relaxing them. Focusing is a skill and a muscle you can train. I wonder if many people habitually don't focus on things precisely, just leaving them a bit fuzzy, and this contributes to the problem?
This sounds you like have hyperopia. This thing you call "focus" is in part accommodation, another part is probably mental concentration. This accommodation ability deteriorates when you are older and develop presbyopia. See https://en.wikipedia.org/wiki/Accommodation_(eye)
What my sibling said too: brightness will lead to sharper vision due to the pin-hole effect.
One aspect of this that I haven't heard anyone talk about is the fact that you can get your eyes to focus more precisely if you practice. You can make out really fine details in something if you have bright enough light and you concentrate on one specific point and try really hard to make it as sharp as possible. You can focus on one ridge of the fingerprints on your hand and then look at the little imperfections on those. Or the individual fibers in a sweater. Likewise you can defocus your eyes just by relaxing them. Focusing is a skill and a muscle you can train. I wonder if many people habitually don't focus on things precisely, just leaving them a bit fuzzy, and this contributes to the problem?