They discuss the potential for block discovery rates to be changed in a softfork and the example of SegWit as proof that massive changes to transaction and block formats can be made with a softfork. However, the only things that cannot be usefully changed in a softfork are the block header format and how proof-of-work is computed from the block header. ZmnSCPxj mentions Taproot's implementation and deployment taking a long time with controversy surrounding the activation code, despite there being no significant controversy about it being an improvement to the network. Any hardforks would have to go through similar hurdles and even a higher hurdle of being a hardfork. Thus, anyone contemplating a hardfork must be prepared to work on it for several years before anyone takes it seriously. There are no quick solutions in this space. Additionally, a potential "emergency" branch has been maintained by one individual to add some kind of post-quantum signature scheme to Bitcoin, in case of a quantum break.