this feeling demands deep personal reflection and / or extended authentic conversation with someone who knows you well -- nothing a text forum will be able to give you so do not be discouraged if you read a hundred posts of advice and none of them do anything for you.
If you want to explore more of the philosophy of this kind of feeling then I have a recommendation. There is a popular podcast called "Philosophize This!" by Stephen West that actually went into a multi-episode dive on "The Creation of Meaning" recently. It starts on Episode 157. The podcast is a casual conversation-style lecture format. The first episode is 25 minutes long.
>Yet we focus on these artificial goals set by childish dreams, society or life events.
In my experience goals are used to resolve unmet needs. Children are very needy and have lots of goals. If you need more money, you set a goal to get it.
Is it possible that you have no goals and see no point in anything you do because you have nowhere to go but down? You are safe. You are fed. You did it. Maybe it is time to kick your feet up and enjoy.