To say don't use Photoshop (or your favorite editing program) is going a bit overboard in my opinion. Let me tell you why.
HTML/CSS, while yes, has the ability to make something that's "real" and clickable, is also slower to work and experiment with, and doesn't easily let you be creative in terms of unconventional layouts and designs. A lot of creativity, at least for me, comes from rapid experimentation and this is what Photoshop allows me to do that no other program has really been able replicate (yes, even Sketch, because you're limited in your options when it comes to working with raster artwork).
So yes, HTML and CSS is great, but for design, it's not the holy grail in my opinion. There are definitely cases where HTML and CSS would be more useful to work with, but for most design work, Photoshop (and Sketch, or equivalent) is still the best option.
To say don't use Photoshop (or your favorite editing program) is going a bit overboard in my opinion. Let me tell you why.
HTML/CSS, while yes, has the ability to make something that's "real" and clickable, is also slower to work and experiment with, and doesn't easily let you be creative in terms of unconventional layouts and designs. A lot of creativity, at least for me, comes from rapid experimentation and this is what Photoshop allows me to do that no other program has really been able replicate (yes, even Sketch, because you're limited in your options when it comes to working with raster artwork).
So yes, HTML and CSS is great, but for design, it's not the holy grail in my opinion. There are definitely cases where HTML and CSS would be more useful to work with, but for most design work, Photoshop (and Sketch, or equivalent) is still the best option.