Yes is a deal breaker without this feature. You need a PC based Thunderbird account or webmail based account to create IMAP folders first. Not found a mobile based e-mail app that doesn't create IMAP folders, only K-9 and now Thunderbird have this fundamental part missing.
Yes, folder creation is an essential part of email management. If I have to do that from my web-based platform only, I lose out on lots of productivity. Let's go!