@pxr5:
As someone who migrated from VDSL-2 with Zen to FTTP with BT, ZyXEL VMG1312-B10A/VMG3925-B10B combination to BT SH-2 I can empathise with your experience, I did implement the move you mentioned, changed the SH-2 SSID & Wi-Fi PW to same as previous, helped a lot with establishing connection to my many network devices withour re-configuration.
I did contemplate using a 3rd party router but as I had opted to retain my land line (now digital voice) it became too complicated.
During my time with BT never had any issues with the SH-2, it just worked and fulfilled all my requirements.
After a 2 year contract with BT I opted to migrate to Vodafone earlier this year, mostly a cost decision and I still wished to retain my digital LL.
For convenience tried to adopt the same trick of SSID/PW migration to the Vodafone Hub, fell foul on this due to PW length rules, had to re-configure all my Wi-Fi devices in the end.
Did discover later that I could have got around this by setting PW on the phone app which ignores the length rule!
Also found the FV Hub to be a lot less friendly with respect to static IP allocation, took a lot of time to configure.
Bottom line, there are much worse ISP provided Hubs/Routers than the BT SH-2.
If you have not opted for digital voice with BT as far as I'am aware there is no reason you can not opt to use a 3rd party router of your choice.
As someone who religiously monitored and recorded my line stat's while on ADSL/VDSL I have found it did take some time to re-program my conception of broadband service with FTTP, accepting it either works 100% or it doesn't work at all