Also, is exporting possible? Let's say I would like to export all text / media to my pc, is that possible?
Any chance you’re accessing your messages from a different device and your main phone is offline?
Whatsapp wasn’t like this before, it was when they introduced E2E that old media started to get lost.
If you want a groupchat with accessible history, whatsapp is not the place sadly.
If you delete your local copy, that's arguably on you – there was never any promise that WhatsApp would be holding your media for re-downloads forever.
I don’t know if you’ve participated in a large group chat, but on those occasions, lots of media is being sent to each other.
I am not that eager to have every media sent in the group chat stored on my Photos library. I don’t think anyone wants that.
So I guess everyone, including me turns off that feature (automatically storing images received), meaning no one will eventually have that image stored on the device which causes the data loss after a while.
Now, there is a backup feature in iOS, but it can only backup to iCloud drive, which I don’t pay for so the limit will be exceeded pretty quickly.
I wouldn’t put the blame on anyone for this, except Whatsapp.
Of course WhatsApp could start charging for storage in the same way that Apple does, but given that WhatsApp is pretty focused on local-only message storage at the moment (similar to Signal, and unlike e.g. Telegram or Facebook Messenger), I don't think that would be a very popular feature.
Either way, I seriously think there is a flaw in the design, especially in the scenario I provided. Had I know that WhatsApp would behave this way beforehand, I wouldn’t have used it.