freebeer (2018-02-07 16:36:15+00:00): Hi, thanks for the long and detailed response, letting us get to know you.
OSM is not just a mapping project, not just a free database, but is in the process forming a community (of freaks ;-).  These conversations are open, as is all the work you do, so if others can benefit from my pointless ramblings, printing them out to line birdcages or something, then all the better.
I'll throw out this URL so you can see how an isolated part of the world not terribly far away from you appears:
https://www.openstreetmap.org/#map=18/34.16021/-117.41181&layers=N
It has its problems of course, just like
https://www.openstreetmap.org/#map=17/55.83289/38.18332&layers=N
which is a bit further away, yet still interesting.
And of course Disney World, which may look great on the screen but is useless for data consumers wanting to do routing.
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There are some issues with everything in this particular changeset of yours, which I'll address later in a followup.
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OSM is, indeed, still in its perpetual infancy.  The US is perhaps in general five to ten years behind the first places to get the sort of detail I take for granted, which I saw going from vast empty space to detailed vegetation mapping.
Your interests are logical; my interest in obtaining the OSM data to put on a cast-off Garmin was to fill out point amenities like drinking water, WCs, and selected shops, things useful to someone cycling for 16 or more hours a day.
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But for now, I took a closer look at what you had done and what data was nearby, and that can be seen at
https://www.openstreetmap.org/node/1419027496#map=19/38.72970/-121.25610&layers=ND
where everything, and not just what PoGo chooses to show you can be seen.
The particular invisible node I highlighted is a cable distribution box, added by the same mapper whose driveways seemed superfluous to you, and I thought to meself, `self, perhaps this is a mapper for a cable plant who also maps minor details applicable, such as drives to represent each residence served by that particular cable distribution point.'
Of course that's not true, but it's a potential use of OSM just as in europe many governments or public transport systems, even businesses (much like Wal*Mart nearer to you) are using OSM as a repository for their data for the public.
PoGo is, for a bit over a year now, just one of the more recent entities who can save a penny by using the OSM data, and sadly the most disruptive, as they do not offer what I describe as a service (like Red Cross rescues in difficult terrain) for the public, but rather entertainment with personal benefits that is too easy to game the system to cheat in ways that very negatively affect the thousands of other users.
I can see a lot of good coming from the flood of players.  There are several new members whose usernames caught my eye at the time, but recently I was pleasantly surprised to notice one of them as one of the top contributors with several thousand items to her/his name one random day, then soon after happened to randomly stumble upon some of those contributions at an area I was investigating.  Work well done.
The problem is that OSM is still in baby shoes in the US and many other parts of the world with a PoGo player population, so those contributions stand out and are easily identified but there just aren't enough eyeballs yet to offer the sort of help I'm happy to give you, that I know won't go to waste.
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There are a lot more than just the two cases of vandalism you refer to.  Generally we OSMlers may call vandalism any deliberately false data, and not just the sort of spray-painting that has always been background noise in OSM, where someone would carefully draw a tree-row, outline it with elaborate shrubbery, add  a few small ponds, and upload that to OSM with description ``HAW HAW PEANUS''.
The particular vandalism you name was not just `DADDY' atop of houses, but rather that five detailed houses with building details were demolished, in their place a park was founded with a couple amenities, and between all the Do Not Tread On The Grass areas were isolated footpaths forming letters on which any park visitor would be stranded, unable to be routed back to safety.
The obvious clues it was Pokemon-related are the priority on parks and footpaths.  That it took two weeks and an anonymous tipoff (whom I think I can thank as a distinguished part of the community) speaks poorly on the penetration of OSM into the general public at present, and the lack of eyeballs to spot that sort of thing over such a vast country.
The second similar case I'm aware of is where a government car park was flooded -- another tell-tale giveaway.  That one was caught quicker, but also demonstrates the level of trust shown new users as well as trust in the community to deal with such issues.
There are countless other cases I've seen, for example if the schoolgrounds southwest of your work here were repeatedly deleted, or military bases removed from the map.
Luckily some days ago a change was made to PoGo so that military is no longer a problem, but the issue that caused you to delete the service drives, or in other places they get changed incorrectly into footpaths, still needs addressing by Niantic, as the fact you can see them (at all) is their issue.
It would also be nice if streams were to be recognised also, as now with water items featuring prominently in PoGo, there is a falsification of data where streams are turned into rivers, deviating from the OSM truth.
So yeah, someone could write a thesis on how PoGo is influencing OSM, more than just our back-and-forth here.
 Probably to be entitled `OSM v. Human Nature: Battle of the Titans' with an anime feature to follow (anna *wicked* soundtrack!).
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Niantic is totally unrelated to OSM except that they suck up the data and base their game on it, and no longer have to pay Google for the maps and data.  They probably could not be bothered what happens to OSM, it falls upon the OSM community to defend itself and its principles (the truth, the whole world is not a park and your mother is not a historic monument), and for the PoGo community to police itself against the abusers, cheaters, those who want to bend the truth for their own benefit by turning their home into a park rather than as originally intended, get outside and active to go to the places with the rewards PoGo players strive for.
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Whew.  Sorry for sounding like your grampaw thar.  That should keep a lot of fish wrapped up as well as litter the streets of this Carneval time (narri, narro, alaaf, hellau, and all that, which reminds me, gotta get outside and act like a fool in public, not just for OSM)
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More on the technical issues to follow.