Re: Cat ... bag ...
The minimum yearly income to retire in France as of last year was €19,237.
Indeed, that's the legal minimum wage (SMIC) before tax/charges, and is the minimum income requirement for a "visa de long séjour". If your visa is for retirement that income cannot come from employment. You also need proof of health insurance. If you've ever worked in France the situation is different.
The full UK state pension for 2022-2023 is £185.15 a week.
If your only income is the UK state pension, or even the French SMIC or state pension, you'll struggle to live in France anyway, especially if you have health issues.
Even so, I think you overstate the official ease of doing so pre-Brexit, anyway. Many people assumed that freedom of movement meant they could just plonk themselves down in any EU country and live there, with no paperwork to do. Especially for Brits in Spain, they just continued to collect their UK pension, and most of the time no-one noticed.
In reality, once you live somewhere for more than 6 months in a year (or leave the UK for more than 6 months in a year) you're likely to find your fiscal residence status has changed. You're then obliged to submit tax returns in the UK & country of residence, and may well have to pay tax in your country of residence and perhaps at home. The rules on which income is taxed where are horribly complex, as are split-year rules, and the subject of many tax treaties. For example, private pensions may be taxable in the country of residence, but government (civil service) ones could still be taxable in the country of source. Property income (buy-to-let) is yet another issue. There's also the question of healthcare, the EHIC/GHIC is only intended for temporary stays. Long-stay residents should sign up with the social services in the country of residence, and have the necessary insurance, many don't bother.
Pre-Brexit many people ignored this, and often no-one noticed, at least until something happened to make it obvious. If someone eventually does notice the result could be a large and unexpected tax bill. Now that a visa is required, of course, the paperwork can no longer be ignored. It should never have been, anyway.