Glasgow scored eight tries in the 52-36 win at the Arms Park, and led 33-12 at the interval, but a fine comeback from Cardiff brought them within striking distance until Warriors pulled away in the final ten minutes.
Cummings picked out the set-piece as an area where there is room for improvement.
"We're a team who believe in ourselves and in our system," said Cummings in The Scotsman. "I think somebody said that the match was probably more brilliant individual stuff than us doing our systems really well. That's all good and well, you've got amazing players who can do amazing things, but at the end of the day it's not long-term success that way.
"We've got to be better at our fundamentals. We didn't do well at some of our lineouts, scrums, stuff like that. Some of that set piece, it's within our control, we can definitely do a bit better in."
Cummings also spoke about his second row colleague, Richie Gray, who announced on Friday that he would be leaving the club at the end of November to take up a new playing opportunity abroad - rumoured to be in Japan.
Gray has been a hugely influential figure over his two spells with Warriors but Cummings believes the young locks at the club are ready to fill the void left when the Scotland international and British & Irish Lion departs.
"Richie has been an amazing player," said Cummings. "He's been around for so long, he's got so much experience and brings so much to the squad.
"But also there's some really good young guys coming up, like big Max (Max Williamson), big Al (Alex Samuel) as well. They're playing unbelievably now, and I believe that they're ready to come in and it's going to be their time coming up as well.
"Obviously he's going to be missed. You can't not miss someone of his quality. But I believe we've got players who can step up into that role."