Evasion requires both area of effect and skill saving in half
D&D rules should be analyzed as simple English: you can write about a "green car" in a sentence, then continue talking about that car in later sentences without the need to repeatedly specify that the car is green. The word "effects" in one sentence refers implicitly to the same "effects" in the following, there is no need to repeatedly specify "area".
In addition, a sentence can be used to limit a definition of a previous sentence. In this case, the first sentence specifies "certain area effects." The second sentence defines what those certain effects are. They are – effects that include a Dexterity save throw for half the damage.
Could it have been written more technically accurate? insuranceone, but that is not a license to selectively ignore one sentence in favor of another, when there is a valid reading that take both sentences into account.
There is nothing beyond the text you have already quoted Evasion, which indicates that it only works on Dexterity-based area effects that allow savings in half. The examples provided are illustrative, not exclusive and complete.
What is an area of effect?
The description of the spell or effect will indicate whether it is an area effect, in most cases using one of several defined forms: line, cone, cube, sphere or cylinder. Enervation, DisintegrateY Immolate may have saved skills, but they are not both area effects Y save in half then Evasion doesn't help Lightning chain it hits multiple targets, but it can be skipped to intermediate people, so it is not an area effect either.
Flaming sphere It is a bit an edge case. Evasion It would definitely not help against the ram, because it is clearly not an area effect. The burn at the end of the shift is debatable and could be discussed in any way; It would be a DM call. I would never call it RAW, but this DM would allow Evasion to work against the burn at the end of the shift, as I see Evasion be the rogue easily and quickly finding a very precise position to avoid the worst part of an area spell, and would count around the edges of Flaming sphereIt's hot how to do just that.
oneI, for my part, would have preferred a more technical / explicit form of writing, but I suspect that the authors of 5E decided that the level of precision in 4E was something that turned people off. I think the pendulum moved too far, and I would have preferred to point closer to 3.5E than the more flexible language with which we ended up in 5E.