I think the reason these sorts of bad practices crop up so often is because internalizing and applying the sort of ego-free principles of Scrum is very very hard, even for a small team (or individual).
Reading that book [0] (particularly the first half) was eye-opening for me, and I recommend it to anyone who works in an "agile" environment.
[0] https://www.amazon.com/Scrum-Doing-Twice-Work-Half/dp/038534...
Edit: I would add that the linked article is pretty typical of things I had read online about Scrum before I read Jeff's book, and I believe are very misleading and unhelpful, as they abuse one way to solve the problems they complain about. Bad team dynamics didn't come from Scrum. Maybe Scrum failed, but that's a whole different discussion.
Errors are the most enriching part of the process and can provide valuable lessons and make you closer to your goal. So don't be afraid to start. Just do it.
Prototyping can be handy to test a few concepts before investing your time coding. invisionapp.com is my fav tool. You can even share the prototype with a group of your target audience/users to get feedback.
If you want to go deeper and learn more about how to focus on your project priorities and productivity, I strongly recommend these books:
https://www.amazon.com/Scrum-Doing-Twice-Work-Half/dp/038534...
https://www.amazon.com/Sprint-Solve-Problems-Test-Ideas/dp/1...
I wish you success on your journey!