In principle it’s a great idea.
My niece did this, and it led to chaos. She’s not very tech savvy, but didn’t want to pay for someone to do it. So she did it herself, and then then they sent out paper invitations with a note of the website.
She hadn’t tested it properly, so it didn’t work. First problem was replies to the invitations. She tried to fix it but couldn’t, so she set up a second website where you could RSVP, and put a link to the second website on the first website.
The RSVPs then worked technically, but not in practice. People were confused. Cue deluge of texts/WhatsApp/Facebook messages to her, her fiancé and his mother, depending on your relationship with the families.
Also, there were no clicky links to the church, reception venue, local accommodation or maps. Would have been dead easy to do, but no. Wasn’t helped by there being two hotels with very similar names, one of which was the reception venue.
The moral of this story is make sure you know what you’re doing and, if you don’t, find someone who does!
I hope you have a lovely wedding. 😘