White has a kind of Stonewall position set up, only the knight is preventing f4...

Looks like White is aiming for a Colle, Black is going for a Queen's Indian, which is the way Capablanca played against Colle.

White is playing the Colle-Zukertort Variation.

A suggestion would be 19...d4 here: It cuts the b2 bishop out of the game while increasing the influence of Black's. The only thing Black would need to watch out for are tactical tricks involving the c1 Rook getting to c7. This might happen for example if [once black plays 19...d4] White later sacrifices a piece on d4 and follows up if Rc7. So long as black remains careful about such tactics then after 19...d4 - he will gradually build up a strong king-side attack.

I noticed some things here. Black's move seems to be quite good to me. Let's see the situation if Black hasn't made his 21st move, and it's White's turn. If Rh1, there is a pin. Black has some options. 1:Qxf4 Nxe4 f or dxe4 Bxe4 the other pawn takes on f4 and White plays g3 attacking Black's DSB and Q at the same time. If Black plays just something, for example a6 (I know it's useless), then White can play g3 even now, losing his DSB or Q again. But it's Black's turn now. He knows these situations can come, but he moves his Q or DSB. So, if he moves Q: Rh3 Be7(or somethting possible move) Bxe4 d or fxe4 and Rg3+, the rook is on the open file, the king is in check... If he moves his bishop, then simply Bxe4 d or fxe4 and Rg3+, again rook on the open file and the king is in check. But with his 21st move Black prevents check if White plays Rg3. That's why my opinion is good of Black's 21st move.

As you said, black is bound to go ahead in his attack, or his king will suffer in such an open castle. For example : 21...Qe6 22.Rh3 Be7 23. Qh5 ! Threatening both Qxh7 and Rg3.

Black's 21st move is in fact a mistake: It is the right general idea and the intention is understandable - but it should have lost the game because of the pawn check e6-e7+ a little later on. [See the note to White's 24th move]. The correct continuation was 21...Rf7. This would have brought Black very good chances because of his greater space and mobility on the king-side.

Now after 23...Rg4 24.Be4! [best] ...dxe4 25.e6+ [and suddenly it is Black who is in serious difficulties. There is no good answer to this little check. White's pieces suddenly become hyperactive. Relatively best is 25...Ke7 26.Ne5 Rag8 - but it isn't enough. In these positions one has to always watch out for clearance sacrifices [the e-pawn vacating e5 to let the knight there] - and this was the reason Black's 19th move was in fact fatally flawed. Having said all that - "Fortune favours the brave."