I have an RME ADI-2 PRO FS and it absolutely does not lack depth. I can digitize LPs and do an ABX comparison and no-one yet has been able to tell the difference. and my system reproduces depth extremely well.I have read and heard in many reviews that the RME lacks depth when playing.
In fact, a couple of those who have heard my system have purchased ADI-2 DACs and their systems don't lack depth either.
Depth perception, amongst other things, is quite dependent on exact level matching. Great care needs to be performed when making the comparison.