Prior to my 2020 LC HE, I owned 3 G wagons, a 2014 G550, 2016 G550, and 2017 G63. They were truly wonderful vehicles and I found the fit and finish to be excellent. All 3 were very solid with pretty much no squeaks or rattles. It should be noted that these aren't built in the same factory that other Mercedes models are built in, so the fit and finish of other Mercedes models is definitely somewhat different. My brother and parents each owned new GLC's in that time period and the fit and finish wasn't as good. Reliability, on the other hand, was not even remotely close to the level Toyota delivers across their entire product range whether it be a Corolla or a Land Cruiser. I traded the G63 in shortly before the factory warranty expired because it was clear that it was going to be $$$$$ to keep it and I'd like to retire at some point

. As mentioned above, G63 brakes don't last very long and are expensive, even without the carbon fiber brakes (those weren't an option on the 2017). Reliability of the new models is also kind of a question mark as a lot has changed, including the engine. The prices have also gone through the roof where a G63 can easily be more than $200K even without any extra dealer markup where a fully loaded G63 was more like $165K in 2017 and you could get a nicely optioned one for around $150K at that point. I haven't driven the new version of the G wagon, but I did "climb around" one as I had initially been considering getting one. They took away a LOT of cargo space in the new model between giving the 2nd row seats more legroom and taking up a ton of space on the sides for subwoofers. The end result is that the cargo space is somewhat lacking in the new G's, which ruled them out for me even if the price increases had not been too much for me to swallow.
The GLC's had reliability issues and my brother now owns a RAV4 and my parents own a Honda CRV. Not surprisingly, the RAV4 and CRV have been pretty much flawless, though not as luxurious as the GLC's were.