If you aren't happy with the quality of the candidates responding to your job postings, it's time to take another look at how you're describing the position and your company. If you put a just a little more thought into how you're writing your postings, you can get a much better response rate which will lead to better hires.
Keep the purpose of the job posting in mind.
A job posting that just describes the job by listing all its responsibilities makes the job sound like work. While prospective hires are interested in the nature of the work, they also want to know about the company and the work environment. The posting needs to make the company sound like a place they want to spend eight hours a day.
Tell the candidate what's in it for them.
Let the candidates know the kind of contribution they'll be making to the company, the industry, or society. Describe the challenges they'll have to overcome and how they'll learn and grow from the experience.
Learn from the way your company markets its products.
Successful companies know that products sell by promoting their benefits, not by listing their features. When you describe your organization and the project you're staffing, think about the ways those qualities will impact the new employee's work experience.
Ask them to think about the kind of person they are.
If you ask a question like "are you the kind of person who…?" you can either draw readers in or lose them at that first sentence. In the case of job ads, this means the prospective employees who read on and answer your ad are more likely to fit in with your organization.
Speak a language they'll understand.
Industry-standard acronyms are fine in tech ads. But using acronyms that refer to internal systems and processes doesn't tell candidates anything. Using language like that makes readers feel excluded and pushes them away.
Make the ad easy to read.
Dense rows of text are intimidating. Make the posting, and your company, appealing by making the listing easy to read. Use a clean font, plenty of whitespace, and bullet points to make details easy to grasp.
Make it easy to respond to the ad.
Online application systems are often very frustrating to candidates. Sometimes information is mandatory when it doesn't need to be. Other times, the candidate needs to upload their resume and then correct errors in how the automated system parsed its contents. Not every candidate will be motivated enough to work through these issues. Maybe you want to weed out unmotivated candidates, but it's usually better to simplify the application process.
You probably have specialists to do your product marketing; you can also use specialists to market your job openings. The cost will be far outweighed by the benefits of a more effective job posting that fills the position quickly.