It's not as simple as you suggest. Changing the dimension means regenerating the thumbnails and for that you need a plugin. If you are developing a site this soon becomes very tedious.
And now make this responsive. Try settings the number of columns for different devices.
Really there is no real difference between wordpress and any other CMS with regards to images. Unless you are using svg images there is a scalability issue. If you are using an existing theme there will be an optimum image size that you will need to use, regardless of cms. If you are developing a theme then, once again there will be an optimum image size.
If you are developing a theme in wordpress then of course you can create as many image sizes as you want and specify the croping behaviour for when they are imported. This way you can use different images sizes in different places. But again there will be an optimum image size to start with.
If you upload an image to Facebook for example, not all original image sizes work well. You have to think about resolution and aspect ratio.
In respect to columns you can do a number of things. It is very easy for a professional web designer to change the number of columns dependent on device. The most common way is of couse to use CSS styling media queries. Alternatively you can use AJAX to update column configuration.
All of these issues are website development issues in general, not specific to any platform.
Choices have to be made during the web design process as to what the site is optimised for. Generally though, given the plethora of different devices and screen resolutions available one needs fluid design.
In web design you can please some of the devices all of the time, all of the devices some of the time but never all of the devices all of the time.