Hi!
possibility to find more results by letting the search engine traverse the "more-general-than" links stored in Wikidata. People have discovered cases where some of these links are not correct (surprise! it's a wiki ;-), and the suggestion was that such glitches would be fixed with higher priority if there would be an application relying on it. But even
The main problem I see here is not that some links are incorrect - which may have bad effects, but it's not the most important issue. The most important one, IMHO, that there's no way to figure out in any scalable and scriptable way what "more-general-than" means for any particular case.
It's different for each type of objects and often inconsistent within the same class (e.g. see confusion between whether "dog" is an animal, a name of the animal, name of the taxon, etc.) It's not that navigating the hierarchy would lead as astray - we're not even there yet to have this problem, because we don't even have a good way to navigate it.
Using instance-of/subclass-of only seems to not be that useful, because a lot of interesting things are not represented in this way - e.g. finding out that Donna Strickland (Q56855591) is a woman (Q467) is impossible using only this hierarchy. We could special-case a bunch of those but given how diverse Wikidata is, I don't think this will ever cover any significant part of the hierarchy unless we find a non-ad-hoc method of doing this.
This also makes it particularly hard to do something like "let's start using it and fix the issues as we discover them", because the main issue here is that we don't have a way to start with anything useful beyond a tiny subset of classes that we can special-case manually. We can't launch a rocket and figure how to build the engine later - having a working engine is a prerequisite to launching the rocket!
There are also significant technical challenges in this - indexing dynamically changing hierarchy is very problematic, and with our approach to ontology anything can be a class, so we'd have to constantly update the hierarchy. But this is more of a technical challenge, which will come after we have some solution for the above.