By all means, that's fine, it's just wrong to say there is no long term data at all on mRNA. It's minimal because it's not been used to any great level before, but what there is has shown no issues.
Also, it shouldn't be forgotten that away from mRNA, there's a whole load of other vaccines expected to report soon enough. From the very traditional 'inactivated virus' ones (where I believe one should be reporting trial results tomorrow), to the other approaches like Novavax and AstraZeneca... The point is, if the issue is 'mRNA is new', there should be an alternative along soon enough.
(The irony is I do know people who would prefer to wait for a 'traditional inactivated vaccine'... when there's actually been notable issues with those in the past, with batches not being sufficiently 'inactivated'. Again, super ridiculously rare, happened a long time ago, and if they prefer that approach then fine, a vaccination is a vaccination. But if 'side effects' is that person's problem, then...)