Instagram Threads app has basically become the Direct app reborn with the newest update that permits messages with anyone, not just close friends
You have two tabs: "close friends" and "everyone else," where you can connect with your close friends while also seeing the messages in your Instagram inbox from other users. Therefore, you may still see other people's messages on Threads whether or not they have downloaded Threads to their phones. The Threads app, on the other hand, will only notify you of messages sent to you by your closest friends. To allow notifications for all messages, you must modify this in the app's settings.
If you've never used Threads before, the app quite works sort of as a private space to allow you to stay connected with only your very close friends and also features a feature to show on auto-statuses including “at home”, “low battery”, etc. Although the app isn’t too popular among people, I have been using it as a private space for just my friends and me. But, the new update hasn't settled well with me since the main purpose of Threads just doesn't exist anymore.
Now, the new update only notifies you of your close friends’ messages by default but this doesn’t help much once you can clearly see another tab 'Everyone Else' right beside it with other messages expecting you. It quite automatically causes you to want to see out those messages. So, during a nutshell, it's now transformed the Instagram Inbox into a standalone app form and therefore the whole point of 'Threads' is thrown out of the window.
Instagram hasn’t released any details about future updates for Threads thus far and everyone that we all know is that the great old Threads that permit you simply interact together with your close friends is gone.