I guess it depends. Did they enter the building via the security line and get properly checked in as is normally required of visitors, or did they waltz in through one of the many broken windows and doors? If the later, they likely broke the law [1] and entered a restricted space, so maybe 'rioter' is an appropriate term for them.
Also worth mentioning, if that same person had a social media history filled with "stop the steal" rhetoric, I don't see why sedition charges couldn't be levied [2]. Even if they were relatively well behaved during the riot, their mere presence was disrupting a central function of government. So I think a well behaved rioter with a proclivity for 'revolutionary' social media discourse can probably be classified as an incompetent insurrectionist.
It will be interesting to see how hard the prosecutors go after these folks. On one hand, a large chunk of the protestors probably got a bit swept up in the moment and likely did not intend to break any laws. But on the other hand, nearly the entire presidential line of succession was in that building performing one of the more important functions of our government. A strong case can be made for showing no leniency.
[1] https://www.law.cornell.edu/uscode/text/18/1752
[2] https://time.com/5928270/capitol-domestic-terrorism/