Is the Czech Defense good?


No. Your premise that you need to catch your opponent off-guard to be successful in chess is flawed, if anything, the fact that your opponents are playing better is a good thing; now you can improve your play against White’s responses to the Caro-Kann more quickly.

I feel that everyone should play whatever opening or defence they like.
I also think that studying openings that you may never actually play increases your ability to play chess.
stay with the Caro kann. it is a grandmaster level defence. it will serve you for your entire life.
you are about to jump a level. and each level how you play the game changes not the game.
example: baseball⚾️. you go from T ball, to little league, to select teams, to high school ball, to college ball, to the minors, and if your lucky the big leagues. or maybe you just get a cup of coffee and call it a career. the game was the same but how you play it changes at each level.

I feel that everyone should play whatever opening or defence they like.
I also think that studying openings that you may never actually play increases your ability to play chess.
stay with the Caro kann. it is a grandmaster level defence. it will serve you for your entire life.
you are about to jump a level. and each level how you play the game changes not the game.
example: baseball⚾️. you go from T ball, to little league, to select teams, to high school ball, to college ball, to the minors, and if your lucky the big leagues. or maybe you just get a cup of coffee and call it a career. the game was the same but how you play it changes at each level.
A similar thing can be said about openings.
At age 21 (1996), I played the Closed Tarrasch, Winawer Poisoned Pawn, Advance with 5...Qb6, main line KIA vs French, Symmetrical Lines in the Exchange.
At age 48 (2023), I have played Closed Tarrasch, Open Tarrasch with 5...Nc6, Open Tarrasch with 5...Nf6, Open Tarrasch with 4...Qxd5, Guimard, Winawer Poisoned Pawn, Winawer with 7...O-O, Winawer with 7...Kf8, Classical, McCutchen, Rubinstein, Fort Knox, Advance with 5...Qb6, Advance with 5...a6, Main line KIA vs French (pawn storm), Symmetrical Exchange, Exchange lines with ...c5, etc.
As you get higher, you expand, not change. Only change what is completely failing for you. If the Caro-Kann isn't broken, don't fix it. It is one of the four legitimate responses to 1.e4 to use for a lifetime, the others being 1...c5, 1...e5, and 1...e6.

"I noticed that everyone knows it and plays comfortably against it."
No one plays 'comfortably' against Scandinavian Qa5.
Here's Master Ly's advice, but I also highly recommend you develop your Own strategy.

Indeed!
There is a high-end Chessable course available dealing with the Czech defense, re-revisited in the 21. century. Alas, in German for the time being. >600 variants, 24 hours video coverage.
Die Tschechische Verteidigung – Rattenscharf Modernisiert (chessable.com)

According to my experience Black is more than on in any of my games.
By the way, a Short & Sweet Version free of charge is also available. In German, for the time being.
https://www.chessable.com/short-sweet-tschechische-verteidigung/course/252041/