Is using the free version of the Canon Pixma Service Mode Tool illegal? Not exactly, but it violates Canon's EULA (End User License Agreement). The DMCA (Digital Millennium Copyright Act) has provisions regarding circumvention of software locks, but repairing a device you own usually falls under "Right to Repair."
Download Version 1.050 only from trusted repair forums. Run it on an isolated PC or a virtual machine. Use it specifically for the "Ink Absorber Counter Reset" on compatible MG3200, MG5200, or iP2700 series printers. And for the love of printing, physically replace your waste ink pads within one month of using the tool.