Jolla Store is restricted in terms of APIs and therefore we don’t have those apps in Jolla store. The restrictions of Jolla store have been made in order to protect users from malicious software, but the consequences of this policy seem quite clear.
Some apps can be installed from various sources, but if installed from Jolla Store, they won’t have all the features they have in e.g. Chum. By the way, there is an old thread you might find helpful.
I believe this is something we all agree with. The current situation of the OS is a consequence of Jolla’s small developer team (around 30 members). If you want to contribute to the development of the OS, you could take part in the community meetings (propose topics or open PRs) and stay active on the forum. Of course, if you have the skills, app development is a great way to gain larger userbase!
EDIT: It is always nice to see new and active users on the forum, keep it up! Sometimes the feedback can be a bit harsh, but I find most people being nice and friendly to each other. 