Interesting debate! As someone who has worked for the french railways, and has good knowledge of the British system, I would agree in some ways with the OP. The flagship long-distance high-speed are the pride and joy of SNCF Mobilités, and as such are second to none in Europe on many levels (except for the restaurant car maybe...). Suburban rail in the Paris area isn't too bad, and considering the price paid by users, is on par with what is available in the south-east of England.
Where french rail is not so great is on regional services, clock-face timetables and high frequencies are still a distant dream on many lines that could justify it, the operating hours aren't that great (most services end around 2000), and to be honest services aren't all that reliable. And certainly if you live in even a slightly rural area you can't count on the railways for your daily transport needs. Most passengers on such lines are captive customers who don't have the choice.
It’s the opposite. No competition planned on high speed lines, only on the regional network.
Open access competition on the french high speed network is absolutely on the cards, and Trenitalia/Thello is widely expected to be the first contender.
Finally someone understands. Absolutely, the regions decide of everything. Even which rolling stock to use.
At the moment they have limited choices, and many are influenced or imposed by SNCF Mobilités. For example rolling stock has to ordered from the limited number of current frame contracts. Obviously once the regions finally get to choose freely their contractor this will change, for the better!