In the relatively short amount of time I've been involved in this hobby and *dabbling* (barely) in higher end gear, these have been my biggest takeaways. When I first became interested in finding out what lay beyond Sony and Bose stuff, I was seeking out YouTubers and the like to tell me what the supposed best gear was. It was a fools errand, though, as most of the reviews / impressions I was reading were of people that listen to music that I never listen to and/or have completely different sonic preferences than I do. Someone who listens to (and reviews gear using) pop, OST's, singer/songwriter type stuff is likely not going to align with me and my library which mostly consist of angry men yelling overtop of heavily distorted guitars and thundering double bass drumming.
I've since figured out who here on Head-Fi listens to similar music genres as I do and also those who prioritize specific sonic qualities similarly to me. It's made it much easier to get an baseline understanding of what gear I might like and what gear may not be for me. At the end of the day nothing will ever beat listening with your own ears and your own library but it's all about understanding where the Head-Fier / reviewer is coming from and their preferences. I take this perspective every time I read impressions here.
As has been mentioned here in the past, we really are in the golden age of portable audio gear. There are so many different flavors, across the entire price spectrum, available today. Once you figure out what you like there are nearly limitless options. IEMs, DAPs, cables, tips... you can tailor to your heart's content.
This is true but imho it goes even deeper than that. Even if you get a circle of people you generally see eye-eye with and whose impressions you relate to even this doesn't diminish the necessity or importance of hearing somegthing for yourself to get a picture of it. Look no further than @drftr's experience-- he meticulously and systematically interrogated everyone and every IEM mentioned in this community for weeks and months and it still took him getting ears on IEMs to actually figure out what he liked. There is nobody-- even people I generally agree with-- who I have not flatly disagreed with about one thing or another. IMHO there are simply too many variables in IEMs and in people's individual listening experiences for anything to really and substantially substitute actually hearing something for yourself. YMMV and all that.