How can a comparative study be novel? I can see several published research papers in SCI journals, even written by undergraduates, that perform a comparative study.
Many of the research papers published under this category evaluate several metrics on the alternative methods that exist in that domain and probably analyze those.
It seems to be just an experimental study followed by comparison. What is the novelty in such papers?
If no novelty exists, then why do good (SCI) journals accept those?
Comparing things is a method.  You cannot judge novelty base on methods.  Novelty is based on conclusions.
For example, if two papers have identical methods but different results leading to different conclusions, they would both be novel.  However, they might not both be correct.