Bear in mind that the 5D4 is not meant to be a high-resolution, base-ISO camera like the 5D2 was, or the D810 and A7r2 are. With the arrival of the 5Ds, that burden's been take off the 5D4. Rather, it is a general-purpose body most suited to event and wedding photographers, who often shoot at higher ISOs (but also sometimes at base ISO with flash or in sunlight), who may shoot a bit of video, need a higher frame rate, etc. The sort of photographer who might use a D750, or, in earlier days, a D700.
Viewed in that light, the 30MP resolution is actually a pretty large jump in resolution from 22MP and the DR is competitive, if not ground-breaking or best-in-class for landscape photographers. For wedding or event use, it certainly looks like it'll beat anything else on the market at the moment, with the possible exception of the D810 (and only if your style is more set shots rather than spontaneous shots). It remains to be seen what Nikon brings out in the D750 and D810 replacements, and how Sony's A9 handles in event photography (sports and fast action are probably a bridge too far at the moment, but events and weddings are an obvious first target in Sony's move from digital back to full-fledged camera system). In any case, it seems likely that the 5D4 will beat the A9 and D810 replacement price-wise, at least.
Really, it's the 5Ds that's the disappointment, not the 5D4. If they made a 50MP sensor with their new, on-chip ADC technology, it'd probably hit the 14-stop DR mark (by DXO's metric, which uses a 1:1 SNR as the baseline). But, being Canon's last sensor based on their old technology, it's essentially crippled as a landscape camera. It holds the resolution advantage (just), but probably not for much longer - Sony's next-generation high-resolution sensor seems almost certain to beat it by 20MP or so, and may even hit the 15-16 stop DR range (possibly with a new RAW format), although the earthquake probably set them back by six months or so. I wouldn't expect the 5Ds to hold to the usual 3- to 4-year product cycle, but, Canon being Canon, anything could happen.