That's assuming that there's a fixed amount of work to be done. If the cost of getting a job done goes down, more people will be interested in that work.

In this case, perhaps you'll have more repeat clients, or more small businesses will choose to make a site than did previously.

Also, since there's likely fewer people needed to do basic design work (even if that market grows), more people would upskill to work on larger applications. My company struggles to find qualified FE engineers, since many are simply web designers. We can and do train them, but ideally we'd have a greater selection of people who already have the skills we're looking for.

Regular maintenance is still necessary, as well as keeping up with modern design standards. And more productivity just means increased sales as long as there are clients present