As a newish player I respect this post on the realities of raiding, but I would like to comment that at least some of the complaints and frustration was likely from people that did not yet have some of the things that enabled the attackers advantage.
For instance, now that I am at SH16, I have mostly a surplus of food for re-rolls but for a while (what felt like a long time) in the beginning it did not feel that way, so I didn’t re-roll much if at all because it seemed like a waste of ham that should be going towards training. This was exacerbated by not having a hero roster that allowed me to pick and choose appropriate heroes for a particular raid either. I had what I had.
When you are pretty much levelling your first set of heroes raiding can so very easily be a frustrating experience. I remember my first weeks trying to raid with 2* heroes and Bane, meeting teams with maxed 3*. Yes, I could eventually fill my raiding chest, but it was quite off-putting. And I’m sure that everyone in a mid to low alliance knows a few players who avoid raiding (and consequently wars) altogether.
So yes please to a practice mode, and yes please to being able to have alliance mates able test your raid and war defense (with war rules).