However, my point is, is Bitcoin development so difficult? Is it a thing from the past? Nobody writes bitcoin-related software anymore? Why on earth isn't there any good bitcoin-related product advertised in the forum?
That's actually a damn good question--and I think the bigger bitcoin "projects" like hardware wallets don't need to advertise on a discussion forum, which honestly seems like an outdated method of drumming up business.
Honestly, I've seen many times that the Bitcointalk community is seen as overly critical and possibly aggressive towards new services. I believe that this is one of the reasons why some new projects do not appear here, they do not want to go through harsh criticism at the very beginning.
Just imagine how much hard work the Ledger Wallet representative here would have to defend all the bad decisions they made in the last year alone. It's clear that they don't need that, it would just make them look even worse.