There is no substitute for repetition when learning a new skill. You just plain have to put in the time to master the new skills and movements that are required to learn an instrument.

But you don't have to spend multiple hours per day to get the job done. You can achieve a lot with 20-30 minutes per day. The critical thing is to get the practice time in every day without fail. That sustained effort makes a big difference over time.

There are some things you can do to make your practice more effective. Something called "interleaved practice" is very helpful. Researchers haves found that when we break up learning into sort segments and rotate between different learning tasks, we learn faster and retain what we learn better. You can search for that online to learn more. There's a book called "Make It Stick" that goes into that in a lot of detail, plus a lot more about how we learn. I'd recommend it to anyone who wants to learn the best ways to learn.

By way of full disclosure, I should probably mention that I learned to play the a saxophone and the flute when I was young, so I did have that base to build on when I was learning guitar. That did help me. But even so, I don't think anyone should rule out learning guitar when they are older if they are willing to put the time in. You may not reach the same peak you might have if you'd been playing all your life, but you can still get good enough to enjoy playing the songs you like.