OP I was you about 14yrs ago, with a dream of baby (and even now, a dream of a teenager) thought I was great! I had it all sorted, such a great (smug) parent telling everyone they just needed to do it my way, and they'd be fine. Never a tantrum. Chose fruit over sweets. Ate a great diet. Always listened when I said no.
Then dd2 came along. She knocked the smug out of me pretty damn fast, I will tell you! She was parented the exact same as her older sister but it didn't work. She didn't sleep after a yr, and I had to lie with her almost every night to get her to sleep FOR YEARS. She wasn't up and about, she just couldn't relax and switch off. She'd wake at 4am and come into our bed FOR YEARS. She would throw almighty "tantrums", her life had to adhere to strict routines (dd1 was so portable, and flexible, weekends away at the drop of a hat etc) and she didn't sleep for more then 5hrs a night. She would hit her head on a wall when upset, claw at her skin until it bled, pulled her hair... She has never hit any one of us. She changed our lives dramatically!
She never drew on walls, played with make up etc. But unless watched like a hawk, she would put non edible items in her mouth (A&E twice for that one), she would climb (OOH dr for smashing her face on a desk), she refused to get dressed, wear shoes, she refuses to eat anything that she has not chosen for meals.
She is autistic. She is amazing, caring, smart, courageous but until she was diagnosed (at 9) I felt like she was my revenge for being smug. She can be very demanding and very high maintenance.
The point of this is that it is NOT always what you do as a parent, a lot of it is down to your child's personality. Dd2 isn't my "revenge" for being smug, but I look back and realise that I was so fucking convinced I had it all made, and that I was better than everyone else, but I just had a placid first born.
So no, the "terrible twos" are not bullshit. Stop trying to make those who have different children to you feel like they are doing it all wrong. That old saying "you have no idea what battles people are facing" line comes to mind.
Be kind. You might be on here one day asking for help, and kids can change over night!!