Q: Why is the review process for my revised submission taking so long?

Ideally, a paper that has received a major revisions decision is sent back to the same set of reviewers. Since they are already familiar with the paper and have made suggestions for improvement, it would be easier for them to understand whether the suggested changes have been satisfactorily incorporated. However, in some cases, the editor may look for new reviewers if he/she feels that a fresh perspective is required.

From what you have mentioned about the status changes and your communication with the journal, I feel that the journal is taking too long to send the paper for peer review. It should not ideally take more than a few weeks for a revised paper to be sent for re-review. I think you should actively follow up with the journal. Write to them every 2 weeks asking for a status update. This will hopefully, make the editor process your manuscript more proactively.

Related reading:

• My revised manuscript has made no progress for over two months. What should I do?
• What to do if the status of remains unchanged after resubmission of the revised manuscript?