Dear Baudewyn,
We appreciate that you posted back and confirmed the scenario with us.
Per your description, it seems that the numbering of ID column will not update automatically when deleting items in SharePoint list.
If so, we have also tested it on our side, when we deleted one item in SharePoint list, the ID column will not update. As shown below:

We can reproduce the same situation as yours. We do understand the inconvenience caused and apologize for it.
Per our search, Power Automate may achieve your requirement. You can use flow to create an ID column in SharePoint list directly. We’d suggest you post the question in Microsoft Power Automate Community - Power Platform Community to double confirm if flow will achieve your requirement, which is specific channel to handle such situation.
n the meantime, personally I completely agree with you, this is indeed a good addition to the current features of SharePoint. It would be definitely ideal if we can update ID column in SharePoint list automativally. Thank you for bring thing to our attention. We sincerely recommend you go to SharePoint Feedback community to provide your feedback: SharePoint · Community (microsoft.com). This is the best platform to let related team hear from you and make the products and services better for you and others.
If my understanding above is not consistent with yours, you can also post back and point that.
Your understanding and patience will be highly appreciated. I hope that you are keeping safe and well!
Sincerely,
Sukie | Microsoft Community Moderator