Task A is hard, task B is not that hard, what can I say? Task B is simpler (easier)?
Because I am afraid it may imply that Task A is simple(easy) but task B is simpler(easier)!!
However, these systems are mainly designed to extract structured data such as a product or a service information from complex web pages. For a simpler task such as extracting the main article from a news website, the features they provide can be excessive.
Based on your comment, it sounds like your main concern is that by saying "Task B is simpler than Task A" you will imply that Task A is simple, when it is not.
If you had just gotten done explaining to me how A is complex, then I would not make that conclusion. You have just given me a baseline understanding of how complex Task A is. When you tell me that Task B is simpler or easier, it should not change my perception of Task A. I simply have a reference point to compare to.
However, if you did want to say that Task B is simpler than Task A, which is also simple, I would instead say,
Task B is even simpler than Task A.
This says to me that Task A is simple, but Task B is even more so.
The first thing that comes to my mind as the opposite of hard meaning "difficult" is easy. Easily is the adverb form as @Victor Bazarov says. (Be careful - hardly is not an adverb form of hard)
Simple, and its opposite, complex, can refer to the complexity of something - a complex task is usually harder than a simple task, but things other than tasks can be simple/complex. Whereas easy/hard usually only refers to tasks or processes.
The adverb hard has the antonym easily. The adjective hard has an antonym easy. The adjective simple's usual antonyms are complex, complicated, elaborate.
The difference in meaning between simpler and easier is probably not too drastic for your use. You can employ either, I think.
