Please don't be personally abrasive in HN comments.

We detached this subthread from https://news.ycombinator.com/item?id=13270113 and marked it off-topic.

So responsive web sites, using ie. bootstrap and picturefill are lazy these days?

Bootstrap was always lazy. The tool was intended for quic prototyping now it is just the replacment for knowning what you are doing. In other cases it's up to you whether you want to provide the best experience or just "this will do".