On an average peer review process lasts 2-4 months which is normal. Generally reviewers are given 7-10 days to respond to reviewer invitation and 15-30 days to submit the review report.
From my experience, it depends on which journal and where it is domiciled. It can take up one year for Scopus Indexed journals. I personally review withing one week.
For them is normal and the reviewer is not under pressure to review and send back. On several occasion I have heard and seen my friends from Malaysian Universities told me they are waiting for a response from a reviewer on their manuscripts for about a year. My thinking is that, there is the politics of it, the interest of a reviewer and the plagiarism checks they put in place to ensure that the manuscript has not been copied from somewhere. Another reason I observe that might lead to delays in the reviews is that all authors must consent to the approval of the manuscript by email. If one author delays response they will have to wait until all the responses are received. So several factors are involved leading to the delays. These are my opinion.
Normally, the first round of peer review should not take more than 1-2 month after the initial assessment period by the journal editor. However, this expectation could be hampered by different factors.
Let us not forget that the peer review task is completely a volunteering task. Reviewers do not get paid for their expertise in assessing and adding to the quality of the paper. For this reason, so many reviewers would take their time before turning back their reports.
Generally, when it comes to finding reviewers for the next article, editors often face an uphill struggle. Review articles, which normally consist of many pages, are usually turned down by most people. Some other papers, whose areas of focus are new or complex could also take some time before finding a reviewer.
All things be equal, most of the delay at times are attributed to journals‘ administrative handling and processing. The reason cannot be far-fetched owing to the numbers of papers which could be under processing at a time.
And just like most of us, we would rather wait to be optimistic in the reality that our papers would be accepted and published in a good journal with high IF. The waiting has become a disagreeable norm.