The three parts that contribute the most to the total scene load time are:
Downloading the scene resources
This depends greatly on the speed of the Internet connection. The total size of your scene resources is 38MB, which means that on a 10Mbit/s connection it will require 30-35 seconds to download all of them, while on a 100Mbit/s connection it will require 3-5 seconds.
To make this part shorter you would have to decrease the size of the scene resources. In your case it would be mostly about the number of triangles, please see below.
Transferring the downloaded scene geometry to the graphics card
The larger the geometry in your scene is, the longer transferring it to the graphics card takes. Your scene has more than 10M triangles, which may account for a few seconds during the scene initialization time.
To make this part shorter you would have to optimize the geometry in your scene, for example by removing or decimating some objects. You can find the most complex objects in your scene by analyzing the object list in the Objects tab. The list is sorted starting from the objects with the highest number of triangles (at each hierarchy level).
Capturing light probe images
Light probe images used to generate reflections are captured and processed in the browser. The more light probes you have, the longer this part will take. There are 6 light probes in your scene, so taking into account your current triangle count, this part may require a few seconds on an average (eg. integrated) GPU.
To make this part shorter, you could try replacing all your light probes with a single one in the center of the scene.