A simple search of Google will not give you the answer to the question as if bunion correctors work. You will see lots of posts and comments by podiatric and orthopedic surgeons saying that they do not work (they make their money by doing bunion surgery) and you see lots of posts and comments by people selling them say that they do work (they make their money by selling them).
So, who should you believe? Should you believe all the testimonials on the sites selling them. They can be fake. Lots of forum and social media posts ask if the work (eg here and here). Some podiatrists have tried to address the issue (eg here).
In these situations, you need to defer to what the unbiased published and peer reviewed scientific research says. Unfortunately there is not a lot to go on here as its not exactly a popular topic for researchers to look into!
There is one study that has looked at this and, yes it showed that bunion correctors do work at correcting bunions. However, it was only done over a 3 month period and its showed on average a 1 degree improvement per month in the angle of the hallux valgus. That is a reasonable outcome. What they study did not show is that if there is further improvement beyond the three months or if you need to keep wearing them to maintain the improvement. Maybe the improvement reverses when the corrector is no longer used.
There are lots of unanswered questions regarding the research on these, so unfortunately opinions is all that is left. There are opinions (eg here) that even if they do not actually correct the bunion or hallux valgus, they are still useful as a physical therapy type intervention to stretch and keep the joint mobile. This is a reasonable opinion and use of these bunion correctors.