Industry and markets are your best option for limited and/or fragmented play time.
- Your current activities are always waiting for you when you login - no need to look for content.
- The markets are competitive but your interaction with other players is asynchronous - you don’t need to be logged in at the same time and you don’t depend on anyone elses schedule.
Nonetheless, the markets in Eve are dynamic and constantly changing because they are player driven. The skill isn’t the mechanics of making stuff but the strategy involved with figuring out what to make, where to sell it and how to price it. The satisfaction is identifying and successfully exploiting opportunities. There is continuous progression - success brings wealth which opens up new opportunities at a higher level.
Most industrial activity takes place in the background - you don’t need to babysit. Stuff will sell faster if you manage your orders but it will still sell as long as you have positioned your order within the market cycle.
The more time you have, the more links in the value chain you can participate in for higher profits but you can buy your inputs, hire couriers to haul stuff, etc… fit the activity to the time you have available.