Earlier quoted context omitted.
What frustrates you about Shopify that you wish could be better?
for example not being able to specify that this product weighs 80 pounds and is shipped in two separate pieces. Shipping 1 large box costs less than shipping 2 boxes half the size and this was making us lose money on automatically calculated UPS shipping fees
There are soooo many different combinations of how you can do certain thing, and in most cases you need to adapt the software to existing process instead of improving it. There was a comment that most of these solutions are slow, know you know why.
We do a lot of integrations with ERP systems and that is another big headache. Their support, not working software, bad or no API support, and their hidden fees are just awful. Then you realize that there are about 10-15 big ERP players in the world, and about 20000 smaller ones (probably every small village has one ERP provider).