First, there's a clear (and artificial) skewing of supply-demand curves. There are probably like 30 (active) guys for every 1 (active) girl on these apps (looking at you, Tinder). This creates an imbalance where women are incredibly selective while men end up being incredibly non-selective (e.g. swipe right on everything). Clearly, this needs to be addressed -- this "marketplace" is a sham.
Second of all, a lot of women (but also men) use dating apps to increase their social following (be it Snapchat or Instagram). This probably only pertains to people in their 20s or 30s, but it's a huge problem when trying to seriously find someone to date.
Third -- the botpocalypse. About 70% of my matches on Tinder this past year (I actually quit all dating apps around 4 months ago) have been bots. Not sure if this is a tractable problem, but after a while, it just gets old. At this point, matching with bots is a meme on /r/Tinder, for example.
Fourth, there needs to be an in-app incentive to meet in real life. I feel that my generation (millennials) are kind of broken. I blow people's minds when I tell them that I work remotely at a coffee shop and started making friends with people there, hanging out, etc. In other words, we absolutely suck at real-life social interaction. So we need these apps to "nudge" in the right direction. A potential solution would be a cross between a meetup and a date.
Fifth, I think hookup culture really is starting to show its dark side. Tinder was very popular as a hookup app a few years ago, but nowadays it's more or less abandoned. People actually want deep and long-lasting connections. None of the apps out there really attempt to solve this. It's a tough problem to solve because building a relationship (like building a friendship) takes time.
Anyway, these are some issues I have with dating apps off the top of my head. I will say that it also probably doesn't help that I live in LA, which is a pretty superficial city to begin with. But the women are gorgeous, so I probably shouldn't complain :)