The performance of the A380 is still not very good, but after replacing the GPU with 16GB of VRAM, it is much better.
I had reduced the texture quality to fit within the 8GB limit, but in fact it was over 10GB, so it seems that there was a performance drop due to the lack of VRAM.
When using a large airport and the A380 together, it can exceed 12GB, so I found that 8GB was far from enough.