Allah is beautiful and He loves beauty but this isn’t the issue here.
Our Prophet salla Allahu alaihi wa sallam has said: if you beautify your Quran and decorate your masjids, then destruction of Allah will fall on you.
At the time of the Prophet salla Allahu alaihi wa sallam, he instructed his companions not to decorate the masjid and he instructed them to make it simple. This is more closer to Allah and it is also more appealing for submissiveness in prayer