I guess for me it depends why they're doing it. I couldn't celebrate living somewhere that rolled back being able to change your sex marker, if doing that was just part of a movement towards enforcing stereotyped sex roles, removing women's rights, denying legal protections against discrimination and harassment to people who consider themselves transgender, or broader conservative changes like anti-homosexual or other discriminatory laws.
In other words, why do the people changing the law want certainty on who's male and who's female, and to emphasise that you can't change that?
Is it because they want law and statistics to reflect reality, and to ensure that sex-based protections and rights are upheld (and, additionally, trans people's rights, since "trans" ceases to have meaning if people don't have an underlying immutable sex)?
Or is it because they think people belong in nice neat gendered boxes, assigned on the basis of their sex, which dictate what kinds of jobs they should do, what role they should have in the household, what part they should play in public life, and whether they should be allowed control over their reproductive system, and that people shouldn't be allowed any route out of those boxes? That it's abhorrent that someone with the good luck to be a man should want to degrade themselves by becoming a woman, or ludicrous that someone born female would have the temerity to pretend that they're a man?
I guess this is what Pluvia was getting at by checking out the political environment there.
I suppose you could argue that a good change is a good change regardless of the political impetus behind it, and that if we get what we want because our opponents (TRAs) drive some of our enemies (sexist, homophobic conservatives and traditionalists) to back the thing we want, and many formerly neutral people to start backing our enemies because our opponents are so extreme, we can take the good and fight the rest later, but it's a risky game to play. The traditionalists will hurt us, and they'll also cause harm to our political opponents on this issue, harm that we don't want and they don't (IMO) deserve.