Doing math is not the same as calculating. LLMs can be very useful in doing math; for calculating they are the wrong tool (and even there they can be very useful, but you ask them to use calculating tools, not to do the calculations themselves—both Claude and ChatGPT are set up to do this).

If you're curious, check out how mathematicians like Robert Ghrist or Terence Tao are using LLMs for math research, both have written about it online repeatedly (along with an increasing number of other researchers).

Apart from assisting with research, their ability on e.g. math olympiad problems is periodically measured and objectively rapidly improving, so this isn't just a matter of opinion.