I totally agree, UK should be included, but this article is based on Eurostat's 2023 dataset which includes all EU member states, three European Free Trade Association (EFTA) countries [Switzerland, Iceland, Norway], and one EU candidate country [Turkey].
Raw data available: https://ec.europa.eu/eurostat/data
It's much harder than it used to be. EU citizens now need a visa to stay and work for longer than a few months, and they mostly need to obtain a Skilled Worker Visa which has occupation and salary requirements.
Since Brexit I've noticed that my London-based employer has had an uptick in hiring Indian and Pakistani nationals, especially in Dev and QA. It's probably not the outcome that most Brexit supporters were gunning for, although I did hear that a large proportion of South Asians did in fact vote to leave for this reason.