The Dragons finished 11th to miss the NRL finals this year, and after losing Zac Lomax and Ben Hunt have been relegated to 2025 wooden spoon favourites by bookmakers.
But Flanagan said all signs point towards the Dragons improving on this year's efforts, putting them on track to play finals in 2025.
The coach said he was "really happy" with the signing of veteran trio Cook, Clint Gutherson and Val Holmes, as well as young halfback Lachlan Ilias.
St George Illawarra head coach Shane Flanagan believes his side can play finals in 2025. (Dean Lewins/AAP PHOTOS)
He said ex-Souths hooker Cook and former Parramatta skipper Gutherson would help fill a leadership void, with the experienced pair possibly sharing the captaincy.
"They're four quality players and we've got Nathan Lawson, who will be on board after his last tournament over with the rugby sevens, and I'm excited about coaching him as well," Flanagan said on Wednesday in Wollongong.
"We're a lot better side than we were last year and we've got some good times ahead hopefully."
In his second year at the helm, Flanagan said pre-season testing was also tangible proof that the Dragons were in better shape ahead of the 2025 season.
"Without a doubt, in all measurements - their strength, their fitness, their speed times, their conditioning - as a group we're a lot better,'' he said.
"Fat content, muscle mass, all those things that our sports science department look after, we're in a lot better starting position."
Cook grew up north of Wollongong and made his NRL debut with the Dragons in 2013, playing two games before a brief stint with the Bulldogs, then the rest of his 216-game career at the Rabbitohs.
"I said to a few of the boys, in my junior footy this was the field you wanted to play on at the end, where all the grand finals were, so some good memories growing up here, it's good to be back," the 33-year-old said.
Damien Cook is delighted to be back with the Dragons, the club where he made his NRL debut. (Dean Lewins/AAP PHOTOS)
Cook said he hoped he could help the Dragons take the next step into the finals, to return to their glory days as premiership contenders.
"Last year they just missed out on the eight, but probably deserved to be there, so hopefully I can do my part, along with the other boys that have come in," the hooker said.
"Their training standards are very high, and they go hard, and these young boys are really challenging us and keeping us on our toes.
"I think we just need to work on our consistency, not just in the game, but also week-to-week, having that standard of finding what we do well and doing that over and over again during the game and then again week-to-week.
"I think that's what you see the great sides at the moment like Penrith are doing really well."
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