I received a similar enquiry by email recently focused on the qualification standards, so I will share elements of my response to that email here.
I will start with the remark that I am sure will be unpopular, but needs saying, which is: my experience of this sort of thing is that wherever you draw the line on anything, the people who are just below the line wonder why the rules cannot state that they are above the line. This is true whether it is FMs in this case, or the 1500-1600 rated players who would like to play in the English Women's Championship this year.
Originally, nobody got free entry to the UK Open Blitz. Then Grandmasters got free entry. Now International Masters get free entry. Maybe it will be extended further in future? At which point, "Why can't CMs get free or discounted entry?" enquiries will land in my inbox.
For the British Championships, why should a FM who is now rated 2100-2199 get a discounted entry - or indeed automatic qualification - versus a CM now rated 2200-2299? Should qualification to a tournament in 2026 be based on what strength a player currently is, or what strength a player used to be? We made the decision to modify it to a rating-based qualification (top 100 in the BICC Federation ranking list, as has been noted elsewhere). This seemed like a fair way to make sure we got the best current players without having people stop playing to preserve their rating, and a number of FMs qualified via this route. From memory, the top 100 cutoff was something in the region of 2250.
We retained GM and IM as a title-based qualification for a specific reason: the Title Regulations allow tournaments with more than 20 foreign rated players, and more than 10 foreign GM/IM/WGM/WIM, to count as a foreign-requirement tournament. FM/WFM do not count for this tournament. This means that for this first time, the English Championships can now be a norm event as the National Championship this year, because the British Championship does not need it. So long as we can get the right strength of fields out for them.
These days, we seem to do a much better job of getting 2200+ players out for the British Championships than we used to a decade ago. The qualification standards are higher as a result, which is really a testament to the improved fortunes of British chess in that period. I don't see this as an effort to demerit the FM title at all; we are just adapting the qualification standards to reflect the current state of the British Championships, and a lot of FMs do still qualify. But we are not in the world anymore with the British that a 2200-rated FM would be in the top half of the tournament.
I realise at this point people - by which I mean Jonathan Rogers - will make their point about the tail, but I will defend that as I did before: there are spots that need to be issued to the British Isles Federations by virtue of it being a British Championships; and there are other qualification spots issued to help events around the British Isles during the course of the year. So as usual, we end up with a compromise between all of these conflicting aims.