Nextcloud is no backup solution: Frequently asked questions (FAQs) around ownCloud
Being a sync solution and no backup solution might be part of the answer why the client does not work like you want it to. Nextcloud is a open source project, contributions to the code ideas etc. are welcome. But please read also the reasoning why the developers designed it the way it is currently. Sure it isn’t perfect, and there is also some discussion about it. And not everybody MUST like and MUST prefer it the way you do!
If you need more support and service, official Nextcloud support could be a suitable option for you. With the money you provide they speed up the implementeation of your preferred features.