One of the challenges in taking writing and publishing advice from other authors is that they usually know only what works/worked for them. An author who has only been publishing for a little while has a very limited experience to draw from.
I understand why published authors want to give advice despite not having expertise—there’s significant pressure on authors to build an audience and other than saying “Buy my book!” which quickly gets old, what else are they going to talk about?
While it may be interesting to read about other people’s querying journey or self-publishing process, authors are not all on the same journey. They will not all have the same results even if all of them do the same thing(s).
Writers sometime treat querying like a numbers game. “I queried fifty agents before I found mine! Don’t give up!”
But it’s only a numbers game in the sense that you have to get your work in front of a lot of people to find the right one. But there is no guarantee that the right person exists or that you will find them. Not all manuscripts and authors will find agents. Sometimes this is because the work isn’t very good. Sometimes it’s because the author isn’t presenting their work effectively. Sometimes the potential audience is too small to make the project salable. Sometimes it’s plain bad luck: you never catch the right person at the right time.
None of that means you should give up after ten tries, but none of it means you’ll be successful after a hundred tries. It is not like rolling the dice where the law of averages says that at some point you’re going to roll sixes.
It is not an even playing field.
So you need to follow the best advice you can, which is usually from agents and AEs who have been in the business for a while. New agents and new editors may be great contacts for you to make but be wary of any expertise they claim to have. Similarly don’t look to literary agents who sell only to traditional publishers for self-publishing advice. Seek the right expert for your goals.