Ohhh, someone with lack of proper impulse control has been offended by an opinion on the internet! Knew someone would get triggered. The fact that it took this long does not speak for you, btw. : - )
What do you mean, what part? “ISK making” is not some specific part of EVE ONLINE. Are you sure you actually understood my post? Feel free to write an essay about how playing video games like they are a job is a fulfilling every day activity, then post it here on the forums.
After exploration? Exploration itself is huge income if your lucky 3-5 bil a day, if you really want to transition into something bigger trading/marketing is the only super massive income, or pvp if your really good and can hunt expensive ship’s.
It’s worth to do exploration as a second job for addition income. It helps to make fast replaces of lost stuff or to make small and fast investments into a bigger business or a new game style. A daily exploration will burn you out from EVE.
As a next step, try Burning Missions, FW with an ALT (a Tier 3 content will give you the same income as Null-Sec/WH exploration per week), Ninja Gas harvesting in WH with Expedition Frigates, a risky Combat Exploration in WH (Defeat and hack Sleeper sites in WH3/4/5) with T3 and the top end Combat Exploration content - farming Sleeper Sites in WH5/6 with a Dreadnaught.