Anyway, I'm wondering if I can be competitive just studying tactics and analyzing games?
First of all, top players don't memorize openings all day. They're extremely good at all parts of the game, even parts people don't write books about... openings are just a tiny part of chess, and a part that most beginners obsess over.
Indeed! Did you see Caruana's round 8 game in the candidates? Impressive endgame skill on display! It took an inaccuracy on his opponents part to win but it was still impressive to me.
What about photographic memory guys? I have a prodigious long-term Collective memory, but my flash memory is not the least bit formidable. I really struggle with games like concentration, but maybe that's because I've never really tried to develop it mentally. Playing without looking at the board seems like an esoteric concept to me. Can one actually learn to play mental chess, or is that a gift you have to pretty much be born with or develop very early on?
It's an acquired skill, unless you have an actual mental disorder where you can't visualize things in your head (forgot what it was called). Photographic memory definitely will help, but not as much as you think.
I have more than my share of psychiatric disorders, but hopefully, God willing, I won't have to add anymore cognitive impairments to the Magna Carta of mental health records. Imagine the state I would be in, if I went full OCD on openings! New York probably. Little joke there to lighten the mood :-)
Among other travails, I have ADHD issues that might stem from a head injury I sustained in a bike accident in my early teens. That doesn't help my short-term memory to be sure, but strangely I think the concussion may well have rewired my brain to strengthen both the eidetic memory and ambidexterity that seems to facilitate a more fluid relationship between the right and left hemispheres. That doesn't even begin to compensate for the quality of life I've given up owing to depression OCD addiction ... but on occasion, I surprise myself. During one especially misguided summer when I thought I was going to be pre-law or carve out some sort of public service career for myself ... I basically memorized all roughly 8000 words of the United States Constitution (admittedly not that impressive alongside Paul morphe committing the entire Louisiana legal code to memory, while he was in law school). Probably took me 36 hours, but if I hadn't screwed around, I could have done it faster.