There are many factors connected with your speed of learning.
AGE: Don't compare yourself with your kids.
TALENT: You cant do nothing about it.
MINDSET: Fear, believes, motivation.
SPORTS EXPIRENCE: Ice skating, roller blades, skateboard, dancing, yoga, slack line, MTB will prepare your balance for skiing.
FITNESS is crucial to minimize risk of injury.
Don't compare yourself with none, invest time and practice. Progress will come!
With basic fitness you can focus to given tasks and think about what movements are you doing. So you can learn with joy and have fun.
With low fitness you will just think how to survive the lesson, prepare your body before ski season and you will have fun by learning.
With thousands tutorials online it is hard to say what is the best, every ski association has some small differences at ski lessons. Don't think one style is better then another, look at it as different paths to the same goal to be better skier.
Finally all information you found here is just fresh up for real person to person lesson. Every skier is specific and alone you cannot see your mistakes so ski instructor will find the best solution for your skiing.