I find it very difficult to understand the difference between them . For example in this sentence: 网上购物能够受到人们的喜爱。
The difference between the two is "tense".
受 - to receive/get/obtain.
受到 - have/has received/gotten/obtained.
Note that 到 is used as a verbal complement to indicate the (successful) completion of an action.
网上购物受到人们的喜爱。- Online shopping has gotten people's love.
网上购物受人们的喜爱。- Online shopping gets people's love.
他佷受到(人们的/大家的)尊重 - He has received broad respect (from the people).
他佷受(人们的/大家的)尊重 - He receives broad respect (from the people).
受 is a standalone verb and able to express more meaning by compounding other word (e.g. 受到， 承受，遭受，接受). In your sentence "网上购物能够受到人们的喜爱。", You can use 受 here to express "to receive" (网上购物能够受人们的喜爱) and it also makes sense. Most people use "受到" instead of "受" to express "to receive" just because "受到" is more narrowly defined.