How do I make this picture more smoother so it looks like the other

[kuba]

Hi, I am trying to recreate a "Logo" i made back in 2017     . For that I used alpha-to-logo filter "Glowing hot". 
I found out that it is not in the version i am using (2.10) so I downloaded .scm file of that to add it back. 
I used the same font but as the glowing effect spreads it makes really pixelated borders     . How can I make it smooth as i did in 2017 ? is it problem with the .scm ? Is it because of the gimp version ? 
I have tried different "effect size" options from 20 - 500 but it is still not that smooth. is there any tool to make it smoother or should I go back to older version of gimp or what can i do ?
Appreciate any answers.  

[Ofnuts]

Before you flatten everything, try putting the layers in Legacy mode.

   

[rich2005]

This script? https://github.com/piksels-and-lines-orc...g-logo.scm

Not exactly the same but not much difference. The attached SVG and running the script, the effect size (pixels) down a bit to 40. You want a neon blue colour originally.

Edit: I get this: https://i.imgur.com/HsBVy1O.mp4