The majority of designers use the same few software packages (a truism of most digital fields), with the same range of functions and parameters, the same trends, all reading the same internet articles, subscribed to the same creative influencers, and being churned out of the same college courses, where they all got taught out of the same text books.
I'll reply to my own [now un-editable] comment to add, by way of balance to that comments somewhat cynical take, that some of the ubiquitous tools and techniques I mentioned have enabled a great many people to participate in these activities, who might otherwise not. The pros and cons of that too are debatable, however I certainly think we can all see some positives in the principle of technology enabling people.
It's increased homogenisation at every level.