This needs addressing.
At the moment, in both Scotland and England, there is a particular process to go through to get a GRC. It takes time and requires psychological assessments and it can be refused. The purpose is two-fold. First to help the patient themselves, so that they can transition to living as if they were the opposite sex with as little trauma as possible. And second to safeguard the general public and in particular women and children from men who would abuse this process to gain access to women's protected spaces for their own predatory purposes. There was the expectation of at least some degree of commitment. If not full sex reassignment surgery then at least taking the hormones of the opposite sex.
Moreover, even after that transition, the person does not become indistinguishable from the opposite sex. They have the protected characteristic of gender reassignment, but not the protected characteristic of being female (in the case of MtF transitioners). It is still legal to exclude them in circumstances where it is necessary and proportionate having regard to the needs of other people - for example from rape crisis centres where the presence of a male person may be extremely distressing to a woman who has been raped.
Now actually while I might quibble with some of the details here (for example I'm very much against falsifying the historical document that is a birth certificate), in principle it's not a bad arrangement. It takes into account not just the needs or desires of the transitioning person but the interests of the rest of society.
The trans rights activists want all that changed. They want all the gatekeeping removed. They describe it as demeaning and humiliating. (Older transsexuals on the other hand say it's essential and is the thing that kept them sane during transition and made them able to live in society as if they were the opposite sex. But nobody is listening to them.) The TRAs want no gatekeeping at all, and want a simple declaration in front of a JP (that's JP, not GP) and signing a form to be all that is required to get a GRC. (After the recent protests by women's rights groups the proposal to put a six-month waiting period in there has been added, but it still doesn't require counselling or psychotherapy and the TRAs are furious about even that.)
Not only is no alteration to the transitioning person's body required, it's becoming extremely unclear what "living as a woman" actually means. Now this has always been problematic, because it relies on the very stereotypes that women find so offensive. Is it only about how you dress? Many women spend their lives in jeans and sweatshirts and trainers. This was always a bone of contention. But now that men can transition without even shaving off their beards it's getting even less clear what transitioning even means. You don't change anything about yourself except you can now get undressed in the ladies changing room and sleep in the women's dormitory in the youth hostel and demand that a female beauty salon wax your balls?
But indeed, the proposals (which the Scottish government still seems determined to railroad through) do make getting a GRC not much more difficult than simply saying "I am a woman", and that is at the very heart of the objections coming from women. This is already law in Canada and some other countries and the rapidly-intensifying bin fires we can see there should be a wakeup call.
But then there's another point. You don't actually need a GRC to live your daily life as if you were the opposite sex, or even to claim that you are the opposite sex and have people treat you in that way. At present only a tiny number of people actually have GRCs. Partly this is beause they were only introduced in about 2009, specifically to allow transwomen to marry men in the days before same=sex marriage was legal. Arguably, what's the point now? But this means that people who transitioned more than ten years ago don't usually have one and often don't even know they exist.
But also, the modern, militant type of transwoman doesn't bother. Again, it's not necessary when challenging any man who claims to be a woman can be framed as transphobia and a hate crime. The people who are loudest in demanding their right to unfettered access to women's protected spaces don't have GRCs and nobody is telling them to shut up and behave like the men they are until they've got one. This is because legally they don't need a GRC to claim trans privilege.
So in practical terms, "changing your gender" absolutely is as simple as saying "I am a woman" even now.
But it goes further than that. People with a GRC do have more privileges than people who just adopt trans status, but then as I said even there the privileges are not absolute. Necessary and proportionate provisions for genuine single-sex services can be made.
The TRAs want all this ended. They are specifically lobbying for all these exceptions in the Equalities Act to be removed, so that there will be absolutely nowhere that a woman can go that a transwoman (now "self-declared", just a few words in front of a JP) can't go. Even more outrageously, while they are lobbying for the removal of the right of a woman to request that a female perform intimate care for her, they are simultaneously lobbying for the right of a trans person to request intimate care from another trans person!
So I think the most helpful thing is to understand what the present legal position is, and what current actual practice is (not the same thing), and what changes to the legal position are being proposed. In effect the TRAs have performed a policy capture exercise and have succeeded in getting many organisations and authorities to behave as if the legal changes they're lobbying for are actually current law. Current law isn't too bad. But the TRAs are driving a coach and horses through it already and want to make their version of reality the legal one. This is what the women's rights groups are opposing.