Here is the reason why you should not blame or hate Dembele !
Tiny thread :

I know he has been shitty in finishing and whatever he does is so bad.
But ask yourself is it really his fault, is he getting what he needs to play his best.

Koeman came in saying that he will play players at there exact positions and here it is grieazman playing at right wing most of the times, De Jong as center back, Dembele at strikers position everything is so irregular.

And the playing style of Barcelona is what is killing Dembele
Barcelona survives on possession in simple words Barca is always crowded in oppositions box
Hence giving no space to a bullet like Dembele to run or shoot proprly
And the last time he got space against Sevilla run &

Dembele is a similar player like mbappe and vinicius, he needs space to run and shoot and you have seen this in mbappe and vinicius case.

You want proof, Dembele at Dortmund was so good because he had space.
Dortmund's playing style is counter attacks exactly opposite to Barca.
and there Dembele got the space to run to shoot and to succeed.
At Barca he has no space for run, last match he literally didn't make 1run

Same can be with Haaland, at Dortmund he has space but at Barca he may not settle well, ofc he will still score cause of his physique and talent.
Barca needs goal scorer like lewa who can score in tight pressure cause Barca and Bayern both play with possession and crowded

So Dembele has no fault and put him at real Madrids vinicius or psg mbappe position he will flourish as beast
Koeman should adopt counter attack for some time cause young players cant Handle so many players around them at yet, one of the big reasons why only Messi is playing good

I hope you understand.
Give Dembele space he will flourish !!