I think I have pretty valuable input on this as I started less than a month ago and have made most of my money through skilling. The money IS out there, but you can't spam 10,000 luminite ore and expect there to be a market for all of it immediately. You need to utilize the Player Listings function in the Grand Exchange and search! Search for potions, ores, bolts, fish, archaeology materials, anything! If you are still having trouble finding anything you could post on the Marketplace forums letting people know you will skill for them, I'm sure with all the people prestiging and pushing 200m's on here someones bound to want archaeology materials or stuff like rune dart tips. As of the time of writing this, someone is buying over 2,000 red chinchompa's for 35k-37k ea. You can pickpocket Ardougne Knights for 13K each pickpocket and with Sticky Fingers Archaeology relic it can be a pretty afk process. So there is money to be made, you just gotta know how to find it.
All this being said, I think naturally bossing will always be better money, and there is not much you can do about that. It's all about supply and demand, some people want good equipment, ECB's for example, and some people want Luminite ore to train. I can go get 1,000 Luminite real quick but there's no guarantee I could get an ECB today, let alone be geared and prepared enough to do ED3, as not everyone can do this. These RNG mechanics for high tier gear will always be more rewarding than skilling, so if you after lots of money, you'll need to PvM, or PvP(lmao, imagine).
In conclusion, you CAN skill to make decent money but if you want big bucks you gotta kill some bosses!