As someone who ran Dragon Heist, and it was actually the first adventure I've ever run for 5E, I find it FANTASTIC.
It definitely gets a bad rap, but it's only uninteresting if you run it EXACTLY like how the book says. What you should do instead, is use the book as an outline, and feel happy to deviate from it and improvise whenever you feel appropriate.
For example, the book includes the lairs of all the final bosses, but if you play the book exactly as the book says, you'll never actually reach those lairs. So instead, you should have the bad guy "win" a fight to gain all the treasure, and the party needs to confront them in their lair (way better cinematic ending).
In my Dragon Heist (Cassalanter villain) campaign, here are the changes I made;
1. Input the small module "Winter's Splendor" (you can google it it's free) for leveling the party from 2 to 3. Also introduces the party to the Cassalanters so they are aware of those characters but don't yet know they are villains. You can use any Dragon Heist module from AL here, or just make something up, but introduce the villain in a non-confrontational way.
2. Have the villains win the stone of Golorr somehow. The PCs should get it first so they know where to find the treasure, but the villains should win it back themselves so they can find it too.
3. When the villains confront the PCs at the treasure hoard, they need to win. Don't kill the PCs, just knock them out, but the villains need to win and claim the treasure for their plans.
4. The PCs then confront the villain in their lair. The villains themselves are quite tough, so don't be afraid to give the PC some backup with a powerful NPC who is against the villains goal (there is at least one NPC opposed to each villain who the PCs can ally with). In my game, the Cassalanters are throwing their big gala which is secretly a ritual that will consume the gold and the partygoers souls.
That's my help, good luck!