Not entirely true. Frodo "uses" the invisibility conferred by the Ring to escape Boromir. Bilbo used the Ring regularly for 60 years, obviously with some side effects. And Gandalf uses magic constantly.
Frankly, I think people who claim Tolkien portrayed magic itself as evil haven't read the books very closely. Magic itself is portrayed as rather ordinary, much as we view technology today. Some can use it more effectively than others, but nobody promotes the idea that all magic is inherently evil.
Magic is portrayed as a tool, which can be used for good or evil, in most cases, as (almost) any tool can. The exception is the Ring, which cannot be used except with evil as the result. (And of course those of the other Rings which have been corrupted by it.)
Sauron and Saruman are evil not because they use magic, but because they use magic for evil. Saruman worked with magic for thousands of years before turning to evil, due originally to a desire to gain more power to do good. The desire to dominate (for whatever reason) is what is truly evil.
Actually, Tolkien has a very libertarian/anarchistic side.
Nicely said, and FWIW, if it were possible to time travel someone from a few hundred years ago to present day, our technolgy would seem like magic to them.