It's almost 8 years. And you have not mentioned whether it's front or back tooth. Crown is not generally indicated for front tooth unless it's broken or largely damaged. If it's the back tooth, after RCT, the tooth will be added with the filling material which will not bear the load when you are chewing. Since you have noted a visible cavity, there is a possibility of filling removal and reinfection.
Next Steps
You should consult an endodontist/root canal specialist to check the tooth. An xray would be taken to see if there is reinfection or decay. if there's infection, ReRCT is indicated followed by immediate capping. if not, only filling followed by capping.
Health Tips
if you don't agree for capping even now, there is a chance of tooth breakage and you end up in removal of tooth.