Hi,
It is a big problem. Most of our work time is eaten up by support and most of the support issues reported are actually not bugs from us but because CSS or view files are not kept up to date.
Even for view files, instead of simply copying the whole content of the view file in your override, it's much smarter to actually include the original view file after modifying the variables used in it, or replacing the HTML after the original view does its thing.
That way, you have a much higher chance of keeping your modifications valid with updates of the component and you get improvments in the views automatically. That goes for HikaShop, but for any other component too.
If you look at the templates listed on
www.hikashop.com/download/templates-for-hikashop.html
almost none of them has made any update to support HikaShop 3's new view files and CSS files in their overrides and thus the templates don't work properly with HikaShop 3 even though it's now been 5 months that the 3 has been released and the first beta of the 3 was in September. It is in fact often easier to use any other template than these to avoid issues with HikaShop 3.
Besides, if you want to style the buttons your way, we've created specific options in the Display tab of the HikaShop configuration so that the merchant can specify the class he wants to use for the buttons. That way, he can easily switching between the CSS of HikaShop or of the template for them.
And as for the grid system, We've made it on purpose different than bootstrap's to be independent of the template so that the listings will be responsive regardless of how the template is made. Again, this is to reduce the support on our end.
In fact, we've had a few intense months fixing all the bugs in HikaShop 3 at the beginning of 2017, but now that it's stable, we notice that even though the sales are going like before, we have a decrease in support and a big part of it is because there are less issues with templates.
And again, I don't see how that's a problem for you. If you want to override the CSS on your template, just copy/paste the CSS from hikashop to your template, modify it and make sure that the template CSS file is after HikaShop's. It will take over HikaShop's CSS automatically.
So really, having CSS file overrides looks more like a way to make it easier for template designers to not do their job properly and increasing work for us than anything else as far as I can see.
I hope you can understand our position.