I'm not an 'expert' but...
Some commentators will approach this from the political angle either that franchising is good or franchising is bad. Trying to be practical, and while recognising that a lot of the detail isn't out there yet, but -
As said in the opening post, many local transport authorities reduced their public transport staff in the post-2010 era, and the skills of implementing new things are often no longer there. The skills over the last decade or so have been more in making cuts, spreading what budget is left ever more thinly, and telling people why things can't be done. (I don't mean this as a criticism of the individuals still there - I have been a local authority public transport officer.) If network planning, marketing and information provision moves from bus companies to franchising authorities, there may be some transfer of people from bus operators to local authorities, though.
A lot of the people who left local authorities post 2010 have either entered retirement, possibly earlier than they had intended, or gone in to something else. Some local authorities that have tried to hire additional people in the last few years to implement Bus Service Improvement Plan (BSIP) measures have advertised a few times and not been able to get anyone. However attractive a role, not many people will consider giving up their current permanent job for a short term contract. The 'Bus Centre of Excellence' is supposed to try and make up some of this ground, but may be too little too late in the BSIP process at least.
There is a lot of uncertainty over what happens next - in terms of the £ 2 fare (initially a short term thing post covid, but kicked down the line several times), and ongoing service support via the 'revenue' stream of BSIP / BSIP+ which runs out at the end of March. And a lot of councils are already in or heading for major financial trouble, so any non-statutory spending (which at the moment includes public transport) seems likely to be under pressure for some years to come.
While recognising that the deregulated market is not perfect, and is variable across the country, I get the feeling that a lot of the thinking behind franchising is trying to solve the problems of maybe 30 years ago. There aren't many areas or corridors where there are excess profits being made by monopoly operators, or where resources are being put in to 'wasteful competition' that could provide cross-subsidised resources for additional services elsewhere.
The attitude towards small / medium enterprise operators also seems stuck in the 1990s, in that they seem to be seen as a nuisance running low quality buses and should be eliminated. Many small operators have kept routes going - and in some cases built them up again - after major operators pulled out. It seems morally wrong that small operators are going get put out of business because they don't have the centralised bidding teams that the big groups will have to prepare bids for big franchises, or the resources to expand to run big franchises.
Local authorities' areas do not match natural bus networks (with the possible exception of the Isle of Wight) and in areas where county councils have been abolished and unitary authorities were set up, the local authority areas often don't match urban areas. The Reading urban area, for example, includes suburbs in the east and south that are in Wokingham borough, and western suburbs that are in West Berkshire. How would any of those three authorities do a franchise? Would neighbouring authorities that might be of different political colour and different financial circumstances be able to agree on a joint franchise?
And where's the money to do it all going to come from? Franchising on its own won't instantly produce London levels of services and fares, however much the politicans point to London. Franchising potentially generates more levels of admin than the current system does, and presumably will pass revenue risk to the franchising authority. The London bus network takes a lot of revenue subsidy.
There is a valid political argument about the extent to which bus services should be run as a commercial business funded by passengers or as a worthwhile public service funded to some extent by local or national taxation, but that doesn't seem to have come up yet. And with the current government talking about black holes and spending cuts, I'm not entirely optimistic about it all.