I think that the term "revolutionise" comes from the fact that Meghan want to bring change for gender/racial equality. I know this is a big stretch, because one could bring change without knocking the whole system down. However, I just want to point out the reasons behind why "revolutionise" was even used in the first place.
For example, "15 Forces For Change" in Vogue cover, chosen by Meghan. As some Meghan critics have pointed out, most of these women were progressive activist, none of them were conservatives. This could possibly explain why they think that the editorial is political (or political bias).
https://www.vogue.co.uk/gallery/forces-for-change-british-vogue-september-issue-cover
Or supported a campaign to decolonise the curriculum in "male, pale and stale" universities
https://www.thetimes.co.uk/article/...at-male-pale-and-stale-universities-p8znzs5gl
Or perhaps Meghan critics associate herself with her and Harry fan group (Sussex Squad), where at least half of them are Republicans and wanted to bring down the monarchy (in the UK and the Commonwealth countries with The Queen as the head of state). Here, I'm talking about the #SussexSquad on twitter, not those who supported Harry and Meghan in moderation.
At one point, Harry and Meghan were closed to the Jeremy Corbyn, according to the book,
Left Out: The Inside Story of Labour Under Corbyn. Jeremy Corbyn has labelled himself as a socialist and a republican, but also mentioned that given the Royal Family's popularity, "it's not a battle that I am fighting". From looking through the extract of the book, the tabloid treatment of Harry and Meghan seem to be the main reason for their friendship towards the Corbyns. Similar political ideologies seem to have come second. Harry & Meghan seems to be close to other moderate left-leaning political leaders, but not right-leaning politicians. However, I would not call Justin Trudeau as a staunch socialist. Too often, being a socialist is associated to stating a revolution to knock down the system.
...hypocrisies of the colonial classes had made her a target for establishment hate. In Sister Juana, Alvarez hoped Meghan might find a kindred spirit. The Corbyns had privately offered sympathy for the duchess's treatment at the hands of the tabloid press, whose misdemeanours they felt similarly familiar with. The following day, the Sussexes sent a personally signed note of 'great thanks to Jeremy and Laura' for their support and said they look forward 'to learn more about her life and works!' Such was Corbyn dislike of the mainstream press that it had even convinced him to moderate his lifelong republicanism
Like other posters have mentioned earlier, Meghan probably was not committed to become a senior working royal in the long-term or even rest of her life (i.e. being politically neutral, fully grasp the role of constitutional monarchy, duty serve the UK citizen regardless of gender, race, class or political opinions). There could be a possibility that she thought she could be lasted for a few years to gain popularity and status before moving back to LA.