Network size will be the main problem. Many many many projects with delightful features have been deployed. Extremely few last because only a few people end up using them. Not to discourage you, but be prepared.

Also, consider how the service will be used for spam. I set up a simple link shortener a few years ago. Like 2015 or maybe earlier. I didn’t advertise it, but spammers still found it and abused it, so I had to take it down (too lazy to create a login system or anything, just decided to abandon it).

Especially an anonymous service will require moderation. Are you prepared to moderate it? Have to report certain illegal content to the proper authorities; and/or authorities might subpoena you for information about postings.

Again, things to consider.

Also, currently, people post to places like reddit and various other places already. So you want to figure out what makes your platform different, better, and attractive to audiences.