従来: an earlier method and the previous product model
Identify the method reviewed because it took too long and the previous model used to compare the new product's weight and portability.
Find the earlier object being named
従来 (じゅうらい) means conventional or previous. In 従来の方法 it modifies the earlier method. In the new-product sentence, 従来より uses the previous product as the basis of comparison.
Keep the two objects distinct. Reviewing a procedure concerns the method, while being lighter and easier to carry concerns the new product in comparison with its previous model.
Time spent on a method and a product comparison
「従来の方法では時間がかかるため、手順を見直した。」 (The conventional method took too long, so we reviewed the procedure.) The time cost of the conventional method prompted the review. 見直した reports that the procedure was reviewed; it does not establish that the earlier method was discarded or that a new procedure was adopted.
「新製品は従来より軽く、持ち運びやすい。」 (The new product is lighter and easier to carry than the previous model.) The new product is the lighter and more portable one. The comparison with 従来より uses the previous model as its reference. No exact difference in weight is supplied.
Retain the comparison's reference
The noun 方法 is stated directly after 従来の. In the product sentence, the reference is the previous model against which the new one is compared. 従来 does not name the new product itself.
An earlier object can serve as a reference without a statement that it has been discarded. Read the reason for reviewing the method and the product comparison as given, without adding a replacement date or a completed adoption of a new procedure.
Which product is the reference for 従来 in the new-product comparison?
Show the answer and why
It is the previous model. The new product is described as lighter and easier to carry, but the sentence gives no exact weight difference.