Orbi RBR50 replacement

If by AX1800 you mean the Netgear Orbi RBK353 package, there is "good news" and "not so good news".

• The Good News is that this product supports WiFi6, which offers better performance for newer devices.  Newer cell phones, laptops, tablets, Chromebooks, etc. now all come with support for WiFi6.***
• The Not So Good News is that to reduce manufacturing cost (and thus market price) the 350 product is a "Dual Band" system rather than a "Tri Band" like the RBR50.  The single 5G WiFi channel is used to support both connections to user devices and connection between the router and satellites.  This is not necessarily a horrible situation.  The first "mesh" WiFi systems were Dual Band and customers seemed happy with them.  As the number of devices increases and WiFi usage increases, this may become a problem.  Certainly any attempt to "move up" toward gigabit internet service would be affected.
• Also, the 350 product is not seeing much change in firmware compared to the other AX products (750, 70, 850, 960).  For example, those products now support adding another WiFi SSID which makes it easier to connect Internet of Things (IoT) devices which struggle to connect when the 2.4G and 5G WiFi channels have identical names.

Every network manufacturer now offers WiFi6 systems at several price points.

*** The "buzz" in WiFi has moved on toward WiFi6E and WiFi7, which are not supported by as many consumer devices (yet).