I agree with that, I was in that exact position when I was first designing my cube. I would look over the most popular cube threads at MTGS, see what they were running, and try to emulate something similar. It wasn't until actually playtesting and seeing things in action that I saw things that I disliked seeing in a game environment where I wanted to make changes. I would definitely advise against beginning cube designers from referencing the more nuanced cubes here for initial design strategy. There would be way too many decisions and concepts deployed that would end up being information overload. It would be the equivalent of introducing someone to MTG by having them play a complicated CMDR deck in a 4 person free-for-all versus a beginner deck designed for teaching.
Absolutely. I've seen a few newer designers trying to emulate the Penny Cubes by throwing in some of the more niche cards like Auriok Salvagers and such without the proper support those cards need.
That said, I don't think a "first cube" needs to be an old MTGS style power cube. I think it is more prudent for one to just xerox an established list exactly and try playing with it before embarking on their own design journey. I think building either version of the Penny Cube or Adam Styborski's Pauper Cube is a good place to start.