It’s mostly your rate-limits tier + size of prompt(s) + network health… I believe they’re working on ways to make it even faster.
Other things you can do is try to use a smaller/faster model. While DALLE2 won’t replace DALLE3, you can get by with GPT-3.5-turbo or gpt-3.5-turbo-instruct sometimes with clever prompting and a one-shot or two-shot …