iwriting reviews is time consuming, unpaid, and doesn’t help the reviewers career. so it takes a while because reviewers are already busy and don’t prioritize writing reviews too much.
quality of the reviews is questionable. 10% of the reviews are through and provide valuable feedback. the remaining 90% are cursory “yeah this is interesting, publish it” or “not interesting/outside scope”.
very very few reviews find and report scientific errors
there are plenty of low cost open access journals run by nonprofits and professional societies. however junior researchers when building their reputation try and publish in journals that are as prestigious as possible, without worrying about cost, apc, open access etc.