I am 2017 applicant, which makes it worse. I did everything there is, including hiring a lawyer for 2 years, and nothing worked. There is no first-come first-serve basis with IRCC, processing order is random. It depends which agent is processing your file, what due dates (to check again) they place on your file, and there are endless # of workflows that your application goes through. I am not an expert on IRCC, I am simply speaking from the perspective of someone who has been waiting for more than 4 years, and went through a lot of communication with them and my lawyer.Yes they should but learning from this forum many 2021 applicants got their citizenship meanwhile people like me from 2019 still waiting to hear some news from CIC.
Best of luck to all, and I hope you don't have to wait as long as I am till today.