But why do you have to play safe? Take risks, learn what works and what doesn't. Is it so important to be able to beat the game completely on your first try? If you have to lower the difficulty on the first couple of playthroughs in order to get your head around all the different ways of approaching encounters then what is wrong with that?
Take chess for example. A relatively simple game in comparison yet for hundreds of years people have and continue to learn and approach it in new ways. The better a game is, the more rewarding it is to put the effort in to learn how to beat it.
You assume I don't know how to play D&D. I do. Very well, in fact. That's my whole point. There is a core set of abilities and capabilities you need on your team no matter what to do well. A party of 4 is going to tend toward sameness from player group to group. Even if you vary by class technically, play style and magic item use will be necessary to make up for your lack of core coverage. You just made my point for me. Which is this: YOU CAN ONLY TAKE RISKS WHEN YOU CAN GO BEYOND THE CORE ASSUMPTION OF THE SYSTEM. That's not "play[ing it] safe." That's not "beat[ing] the game completely on [my] first try." I'm not in either of those camps so do not try to put me there. If you're advocating for ignoring the system and making blatantly stupid choices, that's not risk either. That's insanity.