So true, particularly on mobile. Sadly, responsive pushes this in the wrong direction and is most often massive bloat and and does exactly the opposite of what is essential for mobile. Mobile requires light, fast, and efficient what looks good and works well. So much mobile is just responsive, massive, horribly designed for mobile, slow thanks to responsive bloat, and just a check box checked thanks to responsive yet done with out understanding the basics of mobile and providing a poor mobile offering.
Far too many people designing and developing on the web don’t think mobile they think responsive IS mobile and have no idea how badly they are failing at getting it close to right. These folks need to learn what good mobile design and development is based on the simple principles of mobile: light, fast, and efficient. Many responsive sites are a half a MB. Or much more and 90% of that is JavaScript and responsive cruft.
Responsive works okay if you have little budget, a small site, and tight efficient design. Most of the darlings in the responsive community are slow, often really poor experience on mobile (particularly if used in real mobile environments, which off wifi on over used LTE (clogged up by bloated responsive sites) and on a mobile (a lot of different mobile devices) that often isn’t rendering the page well thanks to heavy JavaScript pushed at it). A large portion of those punching responsive don’t live on their mobile and don’t rely on it. Mobile web is a great option and in these days as mobile is required (thinking clearly through the other options is essential too, but it takes understanding them and how they fit the user’s needs). Mobile is require to get right too.
Responsive is a good hack for taking poor CMSes and pushing them mobile, but not a great way for doing mobile right. Doing mobile web right is often best with site built and design for mobile with none of the cruft and bloat from responsive. Minor JavaScript and using CSS to handle minor responsive needs between different mobile sizes is a really good path forward.
Having a different site for tablets (these are done horribly and often get mobile versions of a site through responsive and nobody took the time to include a tablet or desktop option. If you spend any time in enterprise board rooms you would see most in there have a tablet and are making decisions based on what shows up on the tablet, if you have a poor mobile design offering pushed to tablet that is what is being considered, that is what level the credibility it set to.
Responsive sites on desktop are also a giant mess. The sites that were easy to read and follow have become rectangular Tetris reading modules not designed for reading ease and enjoyment, but are design to be responsive and fit a model that has become very cookie cutter and relatively poor for everybody. The only sites that are decent are product sites, but news and content sites suffer greatly.
The adaptive web approach, if budget allows (cost isn’t that different when iterating with responsive to get design right with the large and many efforts attempted to get the page sizes drastically reduced for mobile in responsive yet never quite getting there), and have a decent CMS that allows for ease of creating different sites for the content served from it (mobile, tablet, and full). Use the adaptive to get what you are designing right for each end use environment.