tactic-training discouraging

Just follow the engine line and you'll realize that Be2 doesn't work.

One could argue that black's LSB on h7 is a much stronger piece than white's LSB, and that this is the reason to trade.

After looking into some of the moves I see that in case of Be2 instead of Bd3, black has a much stronger center control with Be4, threatening the white queen and getting a nice Square in the center of the board. Black may also want to push b4, forcing the knight away from its outpost on c3 (either a4 or b1, both bad squares for a knight in this position). Lastly, black may want to gain a pawn and attack white's weak kingside with Nxg5, following with a capture on h5. Black's LSB does a good job restricting white's kingside movement.

Those are the reasons I see, feel free to criticize me! ;)

@lovlas @ajeramesimo has a point though. Of course the engine tells you that Be2 doesn't work because of b4 but it's not at all trivial: 16. Qxc6 Qd8 17. Be2 b4! 18. Na4 Nd5! 19. Ng2 Rc8! 20. Qxa6 Ra8! 21. Qb5 Ra5! 22. Qc6 Ne7! and eventually recapturing the knight on a4. The exclamation marks in this case means that it's an only video. But that's just 18. Na4, there's also 18. Nb1. Seeing these lines is highly unlikely. Your intuition has to tell you that the knight needs the square on e2.

Is the concept of a good bishop, bad bishop so important when the center is open?
And if you put it on Be2 and look at blacks Bishop which bishop controls more key squares?
And what will happen to your center control once black plays b4?

i see , after b4 the knight Can return to e2 square However The horse can also jump to a4 then c5 , In my opinion, we must move forward instead of backwards , Also the pawn in a6 is Weak

your opponent's light-squared-bishop was much better positioned then yours... equalize the bishops and develop your rook to d3 with tempo... your overall position looks much better then any alternative.

Your intuition should tell you to play Bd3 without spending too much time on Be2 but if you search for the concrete refutation of Be2 you have to calculate very far.

Lichess tactics could be graded, for beginners , for advanced and for experts.... or for checkmates or for winning a piece and so on

@rkwe4477 you get tactics that match your tactics rating. If you get tactics that are really too hard, solve some more so your tactics rating falls to suit your current skill.