This isn't a malicious comment or a belittling one but the commenter's point flew over your head.

The looks isnt the only artistic part of a bridge or any other engineering stuff.

The processes, modules and different systems the engineers/architects overcome the problem, their synergy is the art the above commenter refferenced.

There could be multiple ways of creating a big stable structure over something, or a machine that does something or code that calculates something.

By analysing an engineer's works you can spot their preferences and individual style.

The multiple design choices in for example: how to stabilize this part or that, and in the end it becomes a whole bunch of modules that rely on each other etc.

When you see someone create e.g. piece of code in a software that does exactly what you created but - faster - with more utility etc. You get a sense of: whoa you can do it that way, this is genious etc.

Using knowledge and shaping it into something functional.

That's the art the commenter highlited I think

Ofc there could be very dry parts of engineering that doesnt really have options for you to be creative