Yes. It is copyright infringement. More importantly, the risk of malware is extremely high. Over 95% of "cracked portable software" on public trackers contains active malware.
If you only need the software for a short project, you can download the from Microsoft’s website. This usually gives you 30 days of full functionality. portable download microsoft visio portable
A Comprehensive Guide to Downloading and Using Microsoft Visio Portable Over 95% of "cracked portable software" on public
A portable Microsoft Visio download is a version of the software that can be run from a portable device, such as a USB drive, without requiring installation on a computer. This allows users to take their Visio files and diagrams with them on the go, without having to worry about installing the software on every computer they use. A Comprehensive Guide to Downloading and Using Microsoft
Your diagrams are saved to OneDrive, allowing you to start a project on your laptop and finish it on a tablet or library computer.
If you specifically need a standalone file that runs without installation and is legal/safe, consider these alternatives that offer native portable versions: Draw.io (diagrams.net) : Offers a desktop version
While it may not have every specific stencil that Visio possesses, it is powerful enough for 95% of flowcharts, network diagrams, and wireframes.