Opensource

I fully understand your points, but I'm just going to put these here since it's not as simple as "be google" in the FOSS community.

“Just upload a photo” to some host.

Not everyone has access to just "some host" or wants to deal with the hassle of their TOS, and a FOSS host has the issue of longevity. Data storage and bandwidth all cost money, and if it's not consistently coming in, then you have an issue. I always wondered if registering as a non-profit and then getting hosting as that would change things, but I don't believe so. These big companies and ISPs don't care too much about servicing without monies. Distributed to the users is also out (see Napster, Limewire, most torrents).

A review system that works

Yeah, humans are messy, and people like to spam things with bots because they can. Review systems are hard in general and they would work consistently if ANYONE had them figured out. It's in everyone's best interest for them to, but even with removing bots, it doesn't remove people making new accounts and paying for them to be filled with garbage (see Amazon). It'd be nice to know you can trust all of the reviews, but there is just no true way. Once you found a way, the spammers, bots, and scammers would all start using that one thing and you're back to square one.

API integration for public transport services like DB. Those already do navigation really well, but no routing directions etc.

Oh, how sweet this would be, if all public transportation services had a consistent API structure. I want this so bad for when I travel, but every town hires a new developer, who has their own idea of what the "standard" should be. To keep all of these APIs straight and updated would be a full time career and team surprisingly enough. That's just for the municipalities that have it available. I want this over everything else. If we could just get everyone to agree to a basic standard so we can have a base standard for API calls to these municipalities, that would be great and give people more access to basic necessities wherever they are.

I say all of this, not to crap on your post. I have the same thoughts and wants all the time in the OSS side of the world. I use OSMand when it doesn't crash, or not have data and I don't have time to update things in the moment. I just try to keep supporting the things that I know I can and work around the quirks of them not being a billion dollar company with thousands of employees. I contribute where and when I have time. It's drops in the ocean, but it's something.