I had that experience to an extent with some amateur horn speakers (not DIY). They also had a certain 'character' they imparted to every track... I didn't realize just how bad they were until I put them against the M2s in the same room.As @Duke mentions - diy can be a slippery slope. Though it is a lot easier today, with measurements and dsp.
One part that can be more difficult with an exciting speaker is its ability to present a believeable, smooth rendering where the speaker itself disappears completely. Because it requires some sort of directivity control beyond just mounting a driver on a baffle. Even a simple solution like wider baffle causes issues, because the sound diffract around the edges and creates secondary sound sources. This is easier to achive with small direct radiating domes and cones mounted on small, sculpted/rounded baffles, but then you loose the clarity and solidity of the controlled directivity approach.
Haven't spent enough time with the 4367s to say how they behave, but the M2s sound as transparent as anything I've heard, and just... dissappear.