Newgrange?

I didn't realize that about Newgrange, but it stands to reason that it couldn't handle the volume of visitors if it was in its original state. The whole place is gorgeous, and the visitor center has loads of information and exhibits. Seeing it with a guide would really enhance in the experience, IMO. The MG tour also goes to the Hill of Tara, right?
Maybe try to find a tour that visits other ancient sites? Maybe one that is led by an archeologist or historian? I don't have any ideas about this. One resource for day tours is AirBnB, which offers "experiences" in addition to "stays."

Thank you. It sounds like you have been to Newgrange and enjoyed it. Yes, we are also going to the Hill of Tara on the tour. It sounds from what you're saying that I'll be satisfied with what I see.

There were two sites that we visited in the Bru na Bonne tour. Both are legitimately ancient. You can access the inside of the one called Newgrange on the tour. If I recall correctly, it was discovered and ‘refurbished’ back in the mid 1900s when it was considered appropriate to do something like that. I don’t remember hearing that it was moved from the original site.
The other site is called Knowth and it has not been ‘refurbished’ in the same way. But it’s not open to the public. Archeologists and scientists have been inside though.
I personally thought it was a special thing to go inside Newgrange, regardless. It was a fascinating tour.
We went on the Mary Gibbons bus tour from Dublin and enjoyed it. Keep in mind she is basically providing transportation and historical commentary along the way. You are handed over to the Irish National Trust guides (who were all excellent) for the actual tour of the site. I bring that up because it’s been a point of disappointment for some travelers that I have read here.

Newgrange has been restored, and the restoration has been controversial in the archaeological community:
As part of the restoration, this white quartz façade was rebuilt, and a concrete support wall built behind it in case of a future cairn collapse. This work is controversial among the archaeological community. P. R. Giot described the façade as looking like a "cream cheese cake with dried currants distributed about".[74] Neil Oliver described the reconstruction as "a bit brutal, a bit overdone, kind of like Stalin does the Stone Age".[75] Some critics claim that the Neolithic builders did not have the technology to build a revetment at this angle.
But, it is still an amazing site to visit, and is quite ancient. I don’t think there is any way to know what it would have looked like originally, so the restoration has been done based on research of other similar sites. One thing is certain, though. You wouldn’t be able to visit it at all if it hadn’t been restored. I don’t think it was completely rebuilt. If I recall ( and it’s over 20 years since I was there) it’s the outer facade that is the controversial part of the reconstruction, the rest was still in situ. So, it’s not a completely new construction, but a certainly a restored one.

Newgrange is awesome as well as the other structures at Bru na Boinne. The guides are excellent!

As Anita explains, Newgrange has been restored. This refers to the outside appearance. Inside is the original! Have a read here.

I thoroughly enjoyed the experience. I also visited Nowth which is completely different but complements to Newgrange. If you can it is worth trying to do both.

Many thanks to all of you! I will definitely still plan to go.