Depends on what you mean by “is it possible”. To completely replace it? Sure, but there might be some features that MPLAB has that VSCode + PlatformIO doesn’t offer. I’ve never used MPLAB, so no idea. All the basics regarding code compilation and debugging should be there though.
PlatformIO has general support for PIC32, as stated in the documentation with example projects available. After doing the basic installation you can just start off from the pre-prepared examples or create a new project for your target MCU in the project wizard.
All compilers and packages are installed automatically when PlatformIO detects you use them (e.g., framework = arduino in the platformio.ini), you never have to download a compiler of framework yourself.
If the PIC32 peripheral library is compilabe by pic32-gcc, one can setup a baremetal project with the libraries and needed compiler options in it to create a project that can make use of those librarires.