Lets take a look at this from another angle. According to the Oxford dictionary, the word "celebrity" is defined as:
1A famous person, especially in entertainment or sport.
‘he became a sporting celebrity’
as modifier ‘a celebrity chef’
More example sentencesSynonyms
1.1mass noun The state of being well known.
‘his prestige and celebrity grew’
Although primarily associated in 2017 as people in entertainment and sports, it would also be appropriate to state "Prince William is a more of a royal celebrity than Prince (fill in the blank with a princely name from a more obscure country).
When using the word celebrity, we can usually define it better with an adjective such as a sports celebrity, a TV celebrity, a royal celebrity, a socialite celebrity. Other words that could be used are "stars" and "luminaries". Celebrity and being a celebrity means that they have a certain amount of renown that is notable and known by the masses.
Reflecting back on the Vanity Fair article, one statement does stand out for me where Meghan is asked about the notoriety of her relationship with Harry. She replies:
“We’re two people who are really happy and in love. We were very quietly dating for about six months before it became news, and I was working during that whole time, and the only thing that changed was people’s perception.
Nothing about me changed. I’m still the same person that I am, and I’ve never defined myself by my relationship.”
Meghan is not just proclaiming that they are "in love" but are two individual people that are "in love". The Meghan that Meghan was before she met Harry is the same person she is today. The same with Harry. Neither one of them is seeking to change, alter, transform or change the image of each other. They love each other
because of who they are and not because of what they could be or turn themselves into. This has been a pitfall before in a royal marriage and we don't see this here. It tells me that this couple is very much grounded in reality.
I don't think Harry could ask for a more well grounded, self confident and congenial person to share his life with and all that his life entails. If it takes a "celebrity" to enhance, support and add to the British royal family, in my eyes it is a good thing all around and a very positive asset.