I feel like I would have a really bad time if I spent so long working on my character and it turns out it's ****
Yeah, don't get too attached to any one character. Early on, you'll be "learning by doing" and new players should just dive in, knowing in advance that your character is going to hit a wall, or some new idea will occur to you, or you'll want to try something different.
But also, every quarter a new DLC is released, and you have to start a new character to access the new content. The game is designed to encourage you to start over, again and again, even if you've been playing for years. You keep all of your old characters, so if you make a character you really like, or if a new DLC is just a dud, you can keep playing your old guy/gal.
but also I am highly discouraged by "needing" to put in hours of minmax research.
You don't. In fact, you shouldn't.
The game is split into two main parts: The Story and The Atlas of Worlds.
The 10-chapter story arc (aka "Acts") takes your character up through level 70-75, and is a complete game of its own (on initial release, the 10 Acts was the whole game). Veteran players can "speed run" through the Story Acts in maybe a dozen hours, I think? I'm not sure how fast the fastest players are, but I'm not even close to that fast. I prefer to take my time playing the Acts, even having done it several times. On your first run, learning the game and poking your nose into every nook, I guess it'd probably be 20-30 hours. You could easily spend 100 hours putting 2-3 completely different characters through the Story section and never even reach the Atlas of Worlds.
The Atlas of Worlds (aka "Maps") is the advanced game, and is specifically designed to challenge veteran players. When the game was first released, it didn't even exist yet. When we're talking about our characters stalling out at level 80-88, and using Path of Building to try to sort things out, we're talking about the advanced game.
I don't think tools like Path of Building and poe.ninja are good to even suggest to a new player. They're intended for veteran players trying to tackle the Atlas of Worlds. They presume knowledge of the game, and can be confusing and complicated in their own right.
You could easily play a couple of hundred hours without getting very deep into the advanced game and needing or using any "min/maxing." The game is [flipping] huge. I think I'm on my 8th or 10th character and still haven't seen and done everything.
let's say I played a bunch of PoE, how hard is it to re-skill your character? or are you just screwed?
Not hard. First, your equipment and Skill Gems can always be swapped out whenever you like. You could even do it in the middle of a fight, but that'd be silly. Second, whenever a new DLC (aka "Leagues") is released - roughly every 3 months - all of your existing characters get a full "respec" of all of their skill points.