I've pulled up each of the questions you've posted that have gotten negative scores overall [at the time that I'm writing this post]. Those are
None of these are, in my personal opinion, terrible or even necessarily bad questions. However, all of them seem to have the same problem: it is very difficult to figure out what practical value the questions are meant to serve.
The precise reasons vary (and I'll iterate over each of them specifically so we don't need to generalize), but the essence of the problem is that Stack Exchange fancies itself not just to be a "help desk", so to speak, but also a repository of knowledge and findings. That's why (especially on the RPG.SE Stack) we put a lot of emphasis on editing outdated/obsolete questions in light of new information, or closing questions that we're not sure will have value beyond "am I reading the rules correctly". There have been multiple occasions (recently!) where we've gone back and downvoted highly upvoted/Accepted answers, either because there's something we think that was missed the first time around, or because new information is available that changes the accuracy of the answer.
Downvotes on a question are, to varying degrees, extensions of that policy: if users suspect that a question might not be useful, regardless of whether they strictly believe the question is "off topic" for the site, downvotes are often the expression of that opinion.
Can you enchant player characters' prosthetics permanently?
As the answer to this question demonstrates, there's really not much more to this question than "none of the books say you can do this; ask your DM". There's [at least] two versions of valuable questions that will merit a response of "ask your DM":
- The Rules-As-Written are vague, confusing, or unclear, and "ask your DM" is the shorthand for the well-written explanation the answer gives to justify why the rules don't explicitly instruct you one way or the other how they should operate.
- The question is trying to hash out a specific build or idea, and the solution to their issue depends on some kind of DM fiat or non-Rules-based solution that nonetheless solves a real problem.
This question doesn't really fit into either category.
What type of pike/spear is listed as it's own thing in the PHB?
This question saw quite a lot of editing, from reviewing the edit history. So in this particular case, it seems like the question probably got downvoted based on its original content, and didn't get reappraised because even after it got to a point where it theoretically represented your actual question, it then got closed for being unclear.
It's still not clear what the practical purpose of this question is, and if it's still pressing to you, I recommend you either open a Meta post for it or ask in chat.
Are Draconic Bloodline traits inherited or cultured and develloped?
The issue here is relatively straightforward: it asks "is it possible to gain class features without levels in that class?", and the answer is "No, you have to gain levels in that class". There's some essence of the question that's also about narrative justification, but there's just not much to be gained from it.
Can you create poisons/effects with a Herbalism Kit proficiency?
This question has the same problem: it asks "can an item be used to do something that nothing in the game says it can do?" Related to the first question: sure, "Ask your DM" is technically a valid answer to the question, it's not based on vagaries in the rules.
In particular, a better version of this question might have looked like this instead:
What ways are there to create Poisons?
That version of the question isn't necessarily perfect (I suspect it might get closed for being "too broad" by trigger-happy users) but it's at least a lot closer to being of practical use for other users: I imagine there are lots of campaigns where having access to the ability to produce poisons would be quite beneficial.
One last note on this question: another reason it might have been downvoted was due to lack of research. The Player's Handbook specifies Poisoner's Kit as one of the tools available for purchase in a normal campaign (pg. 154), and the Dungeon Master's Guide has rules for crafting poisons (pg. 258). Asking this kind of question, irrespective of the details (i.e. using an Herbalism Kit), and not explaining why the rules provided in those two books are insufficient for your needs is probably going to seem poorly researched.
What differences are there between spells and creating magical items?
This is a lot like the first question. The only thing I'll add here that wasn't mentioned before is that 5th Edition D&D removed a lot of stuff that created Permanent effects in the world. The Permanency spell from earlier editions is the obvious absence in this edition, but there's lots of other effects where either the ability to make something permanent has been removed; or the ability to make something permanent is extremely particular to the kind of spell being used—like, for example, using the spell Teleportation Circle to create a permanent circle that allows arrival at it.
As a result, questions of the effect "how can I make X permanent in 5th Edition" tend to raise eyebrows, because "making X permanent" is conspicuously something 5th Edition discouraged in a lot of spaces. So that could be an explanation for the downvotes.
How to improve these questions
The biggest thing for submitting a good question to this stack is asking yourself "what am I trying to do?" and focusing on that. Focus on the actual problem you're having, instead of hypothetical problems.
For most of your questions, I'm not sure they could have been salvaged. Again; they're not necessarily bad questions—for example, I could imagine the Dragonic Bloodline question being well received on a more forum-like site—but they don't have practical uses.
What I'm going to recommend instead, if you have questions where the goals are more esoteric or impractical, that you forgo submitting them as questions to the stack and instead just pop in chat and ask them. I promise that those kinds of questions are more on-topic than some discussions we have there...