Been in this business 20 years now and I did it the 'wrong' way first. Applied to the local three years in a row, never got a callback after the interview. Sat around feeling sorry for myself for a few months, then took a helper gig with a smaller shop just to stay moving. Best decision I ever made. Here's what I tell every young guy who gets that rejection letter. First, apply every single year they're open. Tons of guys get in on thier second or third try and nobody cares that it took a while. Second, while you wait, get on with any crew that will teach you. Non-union shops are where alot of future union hands learn to actually run pipe or pull wire, and that expirience counts when you do test again. Third, ask around about the prep classes some locals run for the aptitude test. A lot of guys don't even know those exist.
The gatekeeping stuff people complain about is real, but it's not a life sentence. I eventually got organized in after eight years non-union and came in at a higher scale because I could actually do the work. The guys who let a rejection kill their whole trade plan are the ones who end up bitter. Keep swinging a hammer either way and the door opens eventually.