Do you read them back? Does your code expect property "X" to be on a "Player" object? Do you put a check everywhere for when it doesn't? Do you have default value for objects that were created before new property was added?
All that work could've been done by your database (which is probably has some kind of JSON implementation anyways), but somehow it's a "no-brainer" to implement data consistency at app-level. Okay.
Why would you put checks everywhere a properly written code base would have one module/service that handles the player object and every consumer would use that one module.
e.g. you add a new field and an application level default, then later that default is changed. Now there's no notion of which default the docs that never had the property should be using. Sure, you just need to patch the old docs to set the property where it's missing. But the GPs point was that by not keeping a consistent schema you end up moving the definition of the data into the application, and you need to be very aware of the trade-off.
Personally I'm really happy using postgres and dropping into jsonb when it's the correct model to use. It's the best of both worlds as far as I'm concerned. I've built and worked on systems using nosql solutions that have been migrated back to sql and the data inconsistencies we found have made me very wary of having a primary datastore that doesn't enforce strict constraints.
Though, everybody's use case is different.
Why wouldn't the defaults be in the application? Why wouldn't it be treated like any other piece of business logic in code that should be unit tested?
That being said, I only caught the NoSQL religion about six months ago when I started using Mongo. But SQL Server 2016 has such great support for JSON natively, as long as I'm spending other people's money, I prefer having the best of both worlds.
if (player.hasSomeProp) {
doStuff(player);
}
With "no-brainer" I mean it doesn't take any effort when developing since the representation of the player object in runtime is exactly the same as it's stored in the database.
There are also excellent out-of-the-box support for arrays, enums, custom types, and JS procedures if you so desire. All that comes with consistent syntax, great aggregation functions, JOINs; and all those 43 years of advancement mentioned in general.
Read the docs, you'll be amazed with what you're missing :)
General overview https://www.postgresql.org/docs/current/static/tutorial.html
JSON support specifically https://www.postgresql.org/docs/current/static/datatype-json...
If you just want things as JS objects, you could have a Player table with a column for playerID and a column for the JSON string.
I'm not saying you shouldn't use Mongo/NoSQL, I just think SQLite is an interesting potential choice. (e.g. https://sqlite.org/appfileformat.html)