I have found mining more of a money maker than fishing.
So really my question is, Was I fishing wrong?? Wrong location? Wrong target?
I'm pretty sure you didn't do anything wrong. I have walked both paths as well, although on a quite different way: my fishing is only at 40ish now and I never went into the 'dangerous' places to mine or fish (read, places where a level 75 can get killed if not careful).
There are a few points I have against mining which make me like fishing more.
1) You can easily fish (for money) in places that don't get you killed, even at lower job levels. This opens up fishing for more people than mining does (or at least this was the case a few years ago when I was more active in both mining and fishing events and when not about every player had several lvl75 jobs available).
2) If you are unlucky, a day of mining will only yield you a full inventory of low value products but no big money item. Fishing (as was said by the previous poster) is more constant and will almost always yield you some gil.
3) There is no way to skill up in mining. I like the fact that, next to fishing up items I can sell for gil or craft into something useful, I occasionally also get a skill up. This highly breaks the monotony of fishing, but is totally lacking in mining.
4) There is no competition with fishing. You can have a dozen fisherman standing next to each other in the same spot, yet your performance and gain isn't influenced by it at all. With mining, if you have two or more people competing, it can become very frustrating fast. With decreasing server population, this is less of a problem now, but it used to be a huge issue a few years ago.
5) Efficient mining requires leveling two crafts at least: Smithing and Goldsmithing (unless you want to throw away a ton of relatively useful ores if you can't turn them into ingots). Being two full fletched crafts, you can only level both to 60 (with an additional 40 points to spare). With fishing the only logical choice of craft is Cooking, both of which (cooking and fishing) can be leveled independently to 100 (which is why my main character is a level 100 cook).
6) Both fishing and mining require you to bring a lot of consumables to the working field (be it life bait or pickaxes). Fishing, however, does offer a lot of spots you can get away with lures instead of stacks of bait and if you have cooking leveled, you can craft your own bait on the spot in a gil friendly way (i.e. lower cost to make it yourself than to buy from AH). Sure you can craft your own pickaxes, but that would be a waste of gil and time (and inventory slots tbh). Back in the time where no satchels were available and 50 inventory space was about all you could look at, this was a big issue.
7) Fishing is a static activity. You just stand on the same spot and do your thing. Mining requires a lot of running around. This means that while fishing, you still have the opportunity to participate in LS chat. I never could do so with mining (unless I would just stand idle somewhere to type).
From the arguments above, it should be clear that I never fished or mined for the money. So, purely from the monetary aspect of it, mining could be more efficient than fishing, I don't know (never went after the big gil mining items). I mined because I needed the ores to skill up Smithing and Goldsmithing (and because I liked it more to go after them myself than to just buy them from NPC or AH unless they were dirt cheap and otherwise difficult to get, like tin ore
Likewise I fished for fun, for skill ups and to obtain items to skill up in Cooking and Alchemy (unless again it was a waste of time to fish and not buy the items, like e.g. jellyfish). I rather enjoyed catching my own Gugru Tuna to make my own Tuna Sushi when I was leveling BST.
I know... I'm weird...