In the following sentence:
“现在大家坐上‘复兴号’,不仅更宽敞明亮舒服、速度更快,在车上打电话的信号也更好了,这些都是能感受到的变化。” 丁荣军说,“我们正在研究怎么接入媒体,让视频也能到车上去。”
The relevant part means:
Not only it is more spacious, lighter, and more comfortable, and faster, but the signal of the phone is also better. All of them are the changes you can sense.
Usually, the adjectives are concatenated with a conjunction, such as 和 or 并. But in this case the adjectives are not concatenated with any conjunction, and it is in the form of "ABC", not "A、B和C".
Why does it use no conjunction, and how can I know in which situations it is required to use a conjunction to concatenate adjectives.
Also, does the meaning get different if I add 和 in this case?