I've got the Lightroom 5 version and I am absolutely happy with it, BUT I can't import any RAW files taken with my Canon EOS750d.
Do I really need to buy the Lightroom 6 version only to work with RAW files?
No, you don't really need to buy Lightroom 6 if that is an issue for you. The alternative is to download the free DNG converter from Adobe and use it to convert your CR2 files to the DNG format. Then you can open those DNG files with your Lightroom 5. If it is important to you to work on your original CR2 files then it will be necessary for you to upgrade to Lightroom 6.
Here are the links to the latest DNG Converter downloads, should you decide to go that route:
Lightroom 6 is a $79 upgrade from Lightroom 5: Software & Services
Or, you could subscribe to Lightroom (and get Photoshop too) for $9.99/month: Lightroom and Photoshop | Adobe Creative Cloud Photography plan