I don't think Goth should be cliquish, or that it is at all wrong to use 'Goth' as a label if you like things that are outside the scope of the original 1980's subculture as well as things that are. If you're into commonly overlapping groups like Cyber/EBM, Japanese fashion, Metal, etc. or into completely not-usually-associated-with-goth hobbies like rambling, cookery, various sports, etc. it does not mean you should suddenly have your ability to call yourself 'Goth' revoked, after all, if someone is trying to fit themselves in a narrow box by avoiding all activities outside it as well as actively doing all those things within it, they are not being themselves at all, and being yourself is far more important than being Goth or not being Goth.
Nobody should try to be Goth, they either like that sort of thing, or they don't, and that is all that should be to it. A lot of people get pressure from outside the Gothic community to try and be "normal" and the last thing they need is to get pressure from inside the Gothic community trying to force them down someone else's definition of Goth. Nobody has the right to dictate another person's taste, regardless of decades in the subculture. Also, anyone who has been in the subculture since the 1980's should have the emotional maturity becoming to their age and know better than to mock people for liking bands or fashion outside their tastes, and even if they don't think it truly Goth, they should approach the subject in a positive way (e.g encouraging people to listen to Sisters of Mercy or Bauhaus) instead of a judgemental way. This is common politeness, and no matter how Punk you are, there is a place for it.
Goth has changed over the last 30-ish years, and it has changed a lot, and become an umbrella term for a lot of darker forms of self-expression, and it has mingled with other subcultures, like Visual Kei/J-Rock, and Lolita, and Metal, and while all these groups are different subcultures in their own right, and always will be, they have had an impact on Goth, and personally, I think it is this diversity that is keeping the subculture alive. Goth has gone from being the fans of a small group of bands from the 1970's, 1980's and early 1990's and become a broad, vibrant movement, an umbrella under which people can be their own dark selves, and find avenues to explore. Goth has grown, and this is no bad thing - an influx of new music that doesn't sound like the Post-Punk or Deathrock of the 1980s does not mean that people will stop listening to the original bands, it just means that they'll listen to other things too. These new bands are not calling themselves Goth (not that the original bands called themselves that); they are calling themselves Gothic Metal, or Dark Cabaret or Industrial or EBM, and are making no claims on the original subculture. What they are, though, is influenced by the original subculture and influencing the current subculture as it grows.
Goth, after all, is a mere label that summarises a person's tastes, fashion and lifestyle, it is a name for a broad subculture that is as diverse as its members, and it has never, and will never, be a line in the sand on one side of which is Goth and on the other side of which is everything else. The boundaries of what is and isn't Goth are different for every single Goth, and while there are some that are approximately agreed on, those areas are fuzzy and indistinct.
A lot of people who from the outside are clearly Goth renounce the name, and I think it is partly from this pressure from certain sections of the Goth community to adhere to certain criteria. If you stop calling yourself Goth, you're free to like all the Goth things you previously enjoyed, and yet are at liberty to enjoy anything else too, as you are no longer under pressure to stay within the bounds of Goth. This situation, though, should not arise. Goth should not be a limiting pigeon-hole, it should be an accepting community of dark outsiders, individuals who are outside the mainstream and drawn towards more morbid and unusual artistic expression, especially music and fashion.
There is also an external pressure on professionally Goth members of the subculture - Goth has been identified as a target market, a demographic to sell to, and therefore it is in the commercial interest to pander to an interpretation of that market (and it is only an interpretation because it is coming from outside) and so, as a professionally Goth person or group, for example a band, get more popular, they will come under pressure from those financially involved to stick to a certain brand (or band) image that they assume will be popular and keep fans loyal. Unfortunately this can very easily lead to either selling out or becoming bland and thus being totally counter-productive, or switching target audience to babybats.
What motivates people to be militant about the boundaries of the subculture mystifies me. Received wisdom is that it is fuelled by their own insecurities as regards their subcultural identities, but I'm not sure this really true. I don't think that the arguments over what is and isn't Goth and the judgement of people as their status of Goth or Not Goth is that simple. I think some of it is to do with how broad the subculture has got, and how a lot of people who are very different indeed from the original subculture (e.g cybergoths) identify as Goth, and this isn't something that people who have big hair and danced to strains of The Sisters of Mercy in the '80s do not recognise as part of what they know as their subculture. One thing that should be noted when it comes to these less traditional manifestations of the subculture is that someone who is dressed up as a Cybergoth and dancing to T3RR0R 3RR0R might also be fond of back-combing their hair and dancing to Siouxsie and The Banshees - they are not mutually exclusive.
One very important, and probably obvious point that I shouldn't have to mention but sadly do, is that just because someone doesn't like a band, brand, shop, item of clothing, etc. that does not impact whether or not it is "Goth" or whether or not someone else should like it or think it is good. Opinions are not absolute truth.