There's multiple things you can do in the game, only one of which requires the dreaded Other People:
-Catch 'Em All, obviously. We're up to three generations of Pokemon out there, some common, some much less so. Different 'mons seem to occur in different areas, too - when I go to visit my sibling, I find a whole bundle of Electric-types, which simply don't spawn near me. But you can probably find most things if you look long enough. You can catch some evolutions in the wild, but mostly you evolve them by catching enough of the base version.
The first Pokemon you catch each day gives you an XP bonus, increasing each day for a week before it resets.
-Spinning Pokestops. These provide you with Pokeballs, berries (to make catching/evolving Pokemon easier), and sundry other items. Again, you get bonus items on the first stop each day, including a rare evolution item if you manage 7 days straight.
-Gyms! Gyms have been dramatically improved since launch. Now, if you can beat any Pokemon in there, you reduce its health and power in future battles (unless someone on its team comes to feed it a berry to heal it). That means it's possible for even a low-level player to whittle down a gym by sheer attrition.
Gyms also have six slots available right from the start, which means most gyms on your team that you come across will have an empty slot or two. Pop your Pokemon in, lay down a few berries to heal up the occupants, and move on.
The really good thing is that there's no pressure to maintain occupation of a gym - in fact, you don't want to! When your Pokemon is kicked out, you earn 1 coins per 10 minutes it was in there, up to a maximum of 50... which means that after 8 hours, you're actually rooting for the gym to be beaten by another team! This means that you can go around sticking Pokemon into gyms for theme or amusement reasons, rather than having to use your strongest all the time.
Also, Gyms have integrated Pokestops, an excellent bonus for those of us in rural areas.
-Eggses. You can randomly pop an egg from a Pokestop, up to a maximum of 9. You then pop it in an incubator (you have one infinite incubator, plus can buy more with in-game coins) and walk until it hatches - 2, 5, or 10km. 10km eggs in particular are a good way to get Pokemon you've not seen before - I hatched a Trapinch the other day.
-Raids are the only part that's intended to be multiplayer, and even then you can avoid it. They consist of a giant Pokemon spawning in a gym for one hour, which you take a full team to try and beat. They come graded at anything from 1-5 little monster icons; I'm able to beat a level 3 raid by myself, and getting closer on level 4. No, I'll never be able to capture a Legendary that way without engaging with other people, but for collecting Mawile or Misdreavous, I can pull it off. (Level 1 consists mostly of Magikarp. It's hilariously goofy.)
-Missions - sorry, 'Research' - are a brand-new addition to the game, and come in two types. Field Research pops from Pokestops, and you can have three on the go at one time. You get a reward (usually an item, sometime a Pokemon spawning) for completing one, and after doing so on eight (non-consecutive) days, you get a big reward - including, in my case, Moltres.
There's also special research for Professor Willow, which is the same for everyone; again, it's fairly simple tasks, though some will take longer (one of mine at stage 4 is to get 5 candies from my buddy, which means walking 15km with the game running). You get a reward after each set of three, and the end result is apparently being able to catch Mew.
Is Pokemon Go deep or filled with substance? Probably not. There's no real working towards long-term goals, other than 'catch enough X to evolve it into Y' (I finally managed to evolve Alakazam the other day, for instance). Everything in the game is centred on enabling you to fill out your Pokedex - you fight in the Gym to earn coins to buy incubators to hatch eggs to get Pokemon, you do missions to earn rarer items to [fight in the Gym/catch Pokemon], etc etc. If you have no interest in trying to complete that list of fictional monsters, then the game probably isn't for you.
But if you
do, then seeing that last Abra you need pop up on your screen, catching it in a single ball, and watching it swirl up as it evolves is worth all the time you put into the game. ^_^
hS