This again, is a concept for ADVANCED PLAYERS.
You don't need to "defend" a blind if you're playing a $1/2, $2/4 NL live game against a horrible weak table that doesn't know starting hands or over plays Ace x or just plays an aggressive donk game. In that case, the game boils down to just who makes the LEAST AMOUNT OF MISTAKES and not something like defending a blind.
This is another example of a beginner watching a youtube vid hearing some advanced player or professional player talking about the importance of defending their blind in a $5/10, $10/20 or a cash game where the competition actually has a clue what they're doing/are winning players and the stealer is looking to improve their hourly rate/performance.
THIS IS NOT FOR folks that MAKE HUGE BLUNDERS like I mentioned above or have huge holes in their games. Again, this is not for folks who don't have a clue about the basics of the game, that will play some mediocre hand who hits second pair or top pair with an awful kicker on a board and shoves all in not knowing how to read board texture or having a clue what their opponent plays and doesn't have the discipline to fold hands when they're more than likely behind in a hand.