Am I the only one who doesn't find tactics trainer that useful?

FunBloodyTactic - try the tactics trainer at chesstempo.com as well as the one here. Personally, it helps me to memorize the possible tactics on the pages below and then identify which ones were involved in the puzzle. In one game where I was running low on time, I saw that I could get a quick mate with a position very similar to the Swallow Tail Mate because I recognized the pattern:
https://www.chess.com/article/view/chess-tactics--definitions-and-examples
https://chesstempo.com/tactical-motifs.html

The rating scheme is absolute gibberish; my attention slips and I get an average puzzle wrong, and I loose 12 points, but when I get an equivalent right, it generously awards me 6 points. Unjustifiably ridiculous.

The Chess.com tactics trainer is crapola. The time and points given are skewed. Take a little more time than normal, get the combo right and you might get one or two points, miss the exact variation though often a different one is as good and you're docked 10. There are no alternative variations given and no useful explanations.
Better are books such as Improve Your Chess Tactics: 700 Practical Lessons & Exercises by Yakov Neishtadt, Test Your Chess IQ: First Challenge (Bk. 1), Test Your Chess IQ: Master Challenge (Bk. 2) and Test Your Chess IQ: Grandmaster Challenge (Bk. 3), all by August Livshitz and The Ultimate Chess Puzzle Book by John Emms. These are hardly the only instructive tactics books either.
ADDITION: Lower rated players might try Tactics Time and Tactics Time 2 created by two Colorado players. These titles are available in book or Kindle form. Use the Look Inside feature at Amazon to get an idea what they provide in the way of tactics.
SECOND ADDITION: Don't forget the classic, The Art of Checkmate by Renaud and Kahn

FunBloodyTactic - try the tactics trainer at chesstempo.com as well as the one here. Personally, it helps me to memorize the possible tactics on the pages below and then identify which ones were involved in the puzzle. In one game where I was running low on time, I saw that I could get a quick mate with a position very similar to the Swallow Tail Mate because I recognized the pattern:
https://www.chess.com/article/view/chess-tactics--definitions-and-examples
https://chesstempo.com/tactical-motifs.html
The chess tempo site does provide a little more concrete puzzles.

I don't think most people enjoy tactics training all that much, but if you do it consistently you'll get stronger.

Yes , that's another problem with the tactics trainer.People watch the rating instead of trying to learn.With a book there is no rating and you focus in learning.
Either you have 1200 or 1800 or 2800 tactics trainer rating , it doesn't guarantee you will see the tactic in a real game and that is the critical thing.Focus in understanding the tactics and be sure that you will see them in a game and forget the rating.
A lot of people will check their opponent's profile for the tactics rating. I dont do tactics trainer at the moment fwiw.

A site exist that allows you to decide what "theme" to practise on pins,removing the guard,double attacks,forks etc. one to 99 moves deep (one to three or one to five moves is more practicle) Mate in 1,2,3,4,5,6,7,8,9. all from real games. This site has an endgame trainer.
Another site has a exersise program that helps you learn "patterns" that mate
And finally this site (chess.com) had a download called "guess the move" where you can play over games of your favorite player (Karpov,Fischer,Kasparov) and guess what this player moved in each position.
Books help but remember in a real game no person will stand behind your opponant with a sign that says mate in 2
Please, cite the sources... isn't competition to Chess.com, so, I don't think it is a problem.