Weren't there sales taxes that were abolished when the GST was introduced, though? If I recall correctly, the removal of those taxes resulted in some things being cheaper, other things being more expensive post-GST.
I can't really think of a single person that enjoys paying more for the things they buy, but realistically, if the government wants the revenue, they would have got it by increasing or expanding the sales taxes that were previously in existance, or by doing what they did and introducing a GST instead.
I can't really comment in a genuinely informed manner on the situation with the hobby store you mention because I really don't know the factors that contributed to their closure other than what you have mentioned, but just to be honest, and in no way intending to be disrespectful, on the surface it doesn't sound like the best recipe (i.e. small B&M store, in a specialised field, not a lot of stock; and I'm just speaking as someone who also runs a small, specialised hobby store, but operating online only).
The face of retail has changed in incredibly vast amounts in the last decade alone. Once upon a time, when I wanted some movie merch that never would have been imported here by an Aussie retailer, I had to send away to Hong Kong for a mail order catalogue, wait for it to arrive in the mail, fill out an order page, go to my local post office and purchase a money order in USD, send all that back to Hong Kong, and then wait for a few months for the things I ordered to arrive. I only ever really did that once, but I could do it every single day now, without a second thought. Tax revenue that could once be counted on purely because people couldn't do what we can now, which is to just turn on a computer, click some buttons in the space of a few minutes, and have products on the way, has surely been diminishing as online, overseas purchases increased. If we want to continue to have this option at our fingertips, some concessions have to be made, whether we like it or not.
People talk about having to pay more - yeah, maybe in comparison to the prices we've been enjoying from online overseas retailers in just the last few years, but I bet it's still less than everyone was paying before that was a possibility, and at least this way, some money remains in the country, which has it's own benefits even if it's not one's hip pocket in the moment.
I'm prepared for there to be accusations and insults coming my way from trying to put the situation in a broader perspective, of course, but I feel it's worth mentioning I could well be significantly impacted by this change as a small business owner. I am not registered to collect GST, and all of my imports have been under the $1k threshold, thus providing me with an advantage over bigger businesses who do have to pay / charge GST on imports and sales, but can access bigger bulk discounts by volume purchases. However, now my stock imports will attract GST no matter what, which will require an increase to prices, and in turn may push me over the threshold where I will be required to collect GST, thus increasing my prices even more and potentially having a noticeably negative affect on my sales. I am not thrilled about this prospect, but I am capable of looking beyond my own purse strings, as well.
