For text notes yes (they are decentralized on nostr), as the are stored on multiple relays and can be easily duplicated and spread.

For media (images / video) we are not there yet. I assume you uploaded to nostr.build so your content is only hosted with them. It is still be better than to rely solely on the corporate platforms.

It is not easily solved as there is always storage and bandwidth costs attached with media.  Still, we are working on better storage options (e.g. the blossom protocol) to decentralize media as well.