I really do not know where the problem is.
There are good reasons, why there is only a limited number of core-plugins in obsidian (which are in themselves already quite useful, imho), and even those can be turned of if it pleases you. You can do away with more or less all Plugins, with yaml, with tags, if you like, and rely completely on links, if you wish. And you even dare use different sorts of links, since obsidian interprets most of them. Even if you have 20 plugins cluttering your frontmatter, you can turn them of and work with the remaining functionality. It’s all your choice, which is more than one can say about most of the competitors I know (and that’s saying something).
Still, you have to be aware that every program that works with a linking system, needs some kind of metadata to provide this functionality. The index for that is either in some kind of database that is being maintained by the program and tucked away from the user (doing things you can not control) or in the document itself. Again: You decide.
The obsidian devs have decided to place most of the indexing in plain sight in the .md, by using yaml. (that is, e.g. if you add aliases to a note, and have the links-pane open, you can see obsidian querying for unlinked mentions in real time). Yes, there is an index too, but it seems to be rather compact than extensive.
And in the end, the core idea of a “second brain” is about discovering connections you did not know about. Links you create yourself are all about things you already know. If that’s what you strive for: have fun!
Still, my advice would always be: prefer using plugins and metadata that only facilitate your workflow and give your vault a comprehensive structure. And use other plugins only for special cases. You don not need advanced slides, breadcrumbs, or other plugins that clutter your frontmatter in all your notes, but in some they might be helpful to achieve you goals. It really is all up to you.
Don’t get me wrong, there are numerous elements, where I would have taken different decisions, if I had been asked. But I am not. And I am not developer, so I have, in a way, to live with what I get. And Obsidian is a hell of a way better, than everything I could dream of during my time at university. I still have my notes from that time: full portability, no functionality …
If a different app suites your needs better than Obsidian: take that chance! But do not dream about not being “locked into” some app if you are invested in it. That’s just not possible. For some things you just should take your time to decide, where to invest. There is always some kind of “lock-in”. Most times you are just replacing one lock-in with another. Portability always comes with the price of sacrificing functionality. And there comes a time when dreaming of resetting your brain is just nuts.
But what about the fear of Obsidian “going away” some day? Or one of the devs leaving and taking away the code?
First: Your notes will still be there. So the important part, your work, won’t be gone. No one at obsidian.md ever promised more than that. Obsidian provides a functionality, not knowledge. And this Program can’t just be “shut off” from “somewhere else”. So you will have all the time in the world to continue working while finding another app and transfer your notes.
Second: Even the metadata in your notes will still be available. So every search function in your System will still be useful, if obsidian does not work anymore. But you have to decide: is it your knowledge you care for, or the functionality?
Third: There are a number of devs that are rather invested in Obsidian already. And lots of users that are investing their time in their vaults. Creating another version of Obsidian, open source or else is definitely no rocket science. Its rather fast development cycle is proof of that. In the end it relies completely on publicly available libraries. And the more users of obsidian there are, the more people will look for a replacement. If I were a developer, I would know what to do …
Again: Portability always comes with the price of sacrificing functionality. If that’s what you are interested in, go ahead. It’s all about your choice.
I, for my part, are - for the time being - more than happy for a versatile, open, evolving, and becoming more and more functional app for my knowledge management needs. I am still haunted by the handwritten notes from my classes that I have never touched again …