Calling it deeply flawed is focusing on just one aspect of it. The name just refers to the darkness in our knowledge about what it is. We don't know. It might be a form of matter, it might be a new factor in our equations or something completely different.
- matter chunkiness at the universe-size scale
- rotational discrepancies at the galaxy-scale
yet it seems to be taken as gospel that lambda-CDM explains both. Please correct me if I'm wrong about this.
that discrepancy only exists if one thinks that :
1. the 6th grade formula for total gravitational force and resulting orbital velocity for 2 spherical balls (one having mass of the galaxy, the other - our target star) at large distances accurately describes the gravitation and orbital velocity of a star inside the disk. Well, it is not. One has to integrate/sum over all the stars and matter in the galaxy (though each star's and remote gas region's contribution into the total force toward our target star can be calculated using that 6th grade formula, so no MOND or the likes is needed) to calculate the gravitational force of the whole galaxy acting upon our target star. The disk shape results in the significant "discrepancy" from the "2 spherical balls" model predictions. The thinner the disk the larger the "discrepancy" - more DM as its proponents claim.
2. the galaxies are fixed rotating bodies, and the stars orbit the Bulge on fixed orbits. They aren't. The galaxies evolve with the disk becoming wider and thinner with time (more and more DM/"discrepancy"). Just like a spiral wheel firework. That is exactly what happens when stars' velocity is higher than would be needed to maintain fixed orbit (i.e. what the 6th grade formula would suggest). Btw, that also means that 2 billion years ago when the life appeared on our planet the Solar system was much closer to the Bulge, not in the deserted suburbia that we're right now.