- Most subreddits are hostile to self-promotion of Web stuff. If you're unknown, you're going to have to be socially involved there enough that people know your name. (Though I agree that small subs like /r/esp8266 are begging for self-made content.)

- Related: people don't know your name because it's in small gray text. You're just another comment.

- You need upvotes. A personal directory requires only one upvote.

- You need to be on-topic. Your work may not fit Reddit's categories.

- Reddit mods are generally more like forum mods than librarians.

- Agreevotes do not equal quality. I don't want to overstate this, but I like that I'm not seeing vote counts on personal directories.

Reddit is cool - but it has its own rules and its own culture that goes with it. I personally wouldn't call it 'the modern web directory'. I do think it's less hostile to the Web than many other platforms - and certain subs like /r/InternetIsBeautiful and /r/SpartanWeb do good work.