Thanks for your YAML. All your settings look good, and the blueprint will send the transition value to your light. There are a couple of things to keep in mind.
Not all lights support transitions in the same way. Some lights ignore the transition value sent by Home Assistant or use their own built-in settings instead. For example, I use Shelly dimmers, and the transition is controlled by the Shelly’s own settings. They only allow a maximum transition of 5 seconds (5000 milliseconds), so even if I set a 10 second transition in the blueprint, the light will only fade for up to 5 seconds.
In my case, I simply work within that limit. For example, I can set a 1 second transition for turning the light on and a 5 second transition for turning it off, and the Shelly will perform those transitions correctly. I just know that any transition longer than 5 seconds will be limited to 5 seconds by the dimmer.
This is Shelly settings
On the other hand, I also use WLED lights, which do support the transition value sent by Home Assistant. If I set a 10 second transition in the blueprint, the lights will fade over 10 seconds.
Have a look in your light settings and see what is possible for what you have.
Blacky 