So maybe people in the future can read what we did in our time
It is possible but the real question you need to ask yourself is "wouldn't a blog or a website achieve the same thing?" You could write "messages" in that blog/website and it will remain on the internet for a very long time so that people in the future can read what you wrote.
The difference however is that a blog/website is designed to "store messages" while bitcoin blockchain is not.
I get the impression that the OP wants to store a message that he can prove is unchanged. There is nothing stopping an operator of a website from changing content, or back dating a blog post.
If I understand the blockchain correctly, the data storage is decentralized
This is not quite right. Each (unpruned)node had to download the entire blockchain to work. The data is copied many times, and each node has to store the same information.