Ah yes, the struggles of diaper changes! I totally get how frustrating that can be when it's supposed to be a quick and effortless task.
For resistant toddlers, I've found that giving them a role in the process helps. For instance, you could ask them to help you by passing you the new diaper or wipeys, or even better, distract them with a toy or snack (for those who are past the baby stage). I also make it into more of a game or wrestle playfully with my little one - making oooh and ahhh sounds as if it's a wrestling match. Makes the experience more fun and humorous, and takes their mind off the diaper part.
As for managing expectations, I've come to realize that giving them some autonomy goes a long way in reducing morning or pre-outing meltdowns. Letting them pick between two outfits you select can help reduce tantrums about clothing choices, and also lets them express their style preferences early on (within reason, of course). Explaining the steps and timeline of your morning routine might also help set expectations and prepare them mentally for what's ahead, giving them some warning to get ready.
These may not be full-proof methods, but they've certainly helped make things more manageable!