Yea i had a feeling that you came from an mmo 
Thats where sources like maxroll comes in handy. They have detailed subsections for leveling builds.
https://maxroll.gg/d4/build-guides?filter[build_guide_type][filters][0][taxonomy]=taxonomies.build_guide_type&filter[build_guide_type][filters][0][value]=archive&filter[build_guide_type][filters][0][operation]=!%3D&filter[build_guide_type][filters][1][taxonomy]=taxonomies.build_guide_type&filter[build_guide_type][filters][1][value]=%20&filter[build_guide_type][filters][1][operation]=NOT%20EXISTS&filter[metas][taxonomy]=taxonomies.metas&filter[metas][value]=d4-leveling
Weird link, but should take you directly to the lvling builds.
However, thats also nothing you really have to worry about while doing the campaign. Just play arround with your char, and get used to the game =) You can get the campaign done with literally no build at all. Some may not enjoy the campaign as you will see here on the forums, but you might see that differently, as you come from an MMO. Its also good to really just get into the game. As i said, theres no need to hurry. Youll worry about “endgame stuff” soon enough =)
well its youtube, so the answer is easy: Clickbait
good point, thats for example something you for sure can put energy into. You only need to unlock these once, and now is a great time to do it.
What exactly is cringe about being new to a game?