just my two cents here - surely the issue with trials is how they are run?
No system is ever going to 100% get the best players picked - so trials if run well are a good way to get a fairly accurate idea of your talent in a short space of time. Trials run poorly of course are not ideal.
Trials in my experience rely on two things. A general outline of how players are looked at, IE what skills should be looked for and secondly you need to have a good amount of spotters and ideally the coach of the team is not the only spotter - IE if you are trialing for an entire age group (say 14th grade) that the 14th grade coach is not your only spotter and he is not the person with overall selection calls otherwise bias comes into it.
My other gripe through Junior leagues was that there was no continuity or communication between years. We're talking 9/10/11/12 sort of years here (I can't remember exactly), but I spent 2 or 3 years in my club's 2nds for whatever age group it was at the time. Player of the year, most goals, whatever you like each year. But have one average trial the following March and everything from the previous season is forgotten. Why coaches don't communicate within clubs I don't know. My other clubs are better?
In my personal case, the same year I made the 1st team was the same year I made the club's academy (1 or 2 players from each year group).