doesn't that solve one of the problems with bitcoin which is a decentralized way to store bitcoin core?
Of course not. Storing a binary alone will not make it decentralized. If someone will upload Windows 10 ISO on-chain, does it mean Windows will be decentralized?
github is not decentralized. it's a central point of failure.
Putting everything on-chain will not make it decentralized. Instead, it will cause blockchain growth, and mempool growth, and as a consequence, you will see less full archival nodes, and more pruned nodes. Do you have a full node, that can store hundreds of gigabytes now? Imagine we switch to terabytes, how many people will switch to SPV nodes or enable pruning, because they won't be willing to store all of those additional data?
Combine it with the fact that
Bitcoin Core is working on a simplified Initial Blockchain Download, based on UTXOs. If people will put more data on-chain, then you will see more nodes, that will store only UTXO database, and nothing else, because
that is sufficient to move chain forward, and that will allow to run a node in adversarial environment of exploding mempool. For example, read those posts in the context of the congested network, and think, if people will switch to such node, if their old software will spend a lot of time on processing data:
Assumeutxo allows a node to start with a preset UTXO set (provided by the user, and does not necessarily correspond to a hardcoded hash in the binary, this detail has not been worked out yet). This UTXO set is the state of the chain at a particular block hash and height. The node can then begin syncing from that particular block. The idea is that the block will be recent, so the node will be caught up to tip very quickly, thus allowing the user to make and receive transactions way faster than if they had to wait for the entire blockchain to sync.
That isn't a use case for *Bitcoin* in that it's something Bitcoin doesn't actually accommodate on a fundamental basis: Bitcoin nodes don't need to store or provide access to historical blocks to operate. They only do today (to the extent they do, many don't) to aid new nodes coming up securely, but in the future that will be accomplished via other means because transferring terabytes of blockchain to process and throw away whenever someone starts a new node won't be sufficiently viable.
it's not free to make an inscription. they do have to pay
Only if that transaction is broadcasted in P2P way to other nodes. In case of almost 4 MB transaction that started Ordinals, it was mined by Luxor. One pool with sufficient hashrate is enough to make the chain bigger. Attackers could reach 1% of the hashrate, and then they can put a lot of inscriptions for free every 100 blocks.