Totally agreed string / text processing is lacking in AppleScript. I’m using RegexStuffAndLib for things like regex matching, string conversion etc. It’s really nicely made (including a dictionary) by Shane Stanley (author of Script Debugger). See RegexAndStuffLib Script Library - AppleScript - Late Night Software Ltd.
I’ve used it quite extensively in my Markdown / Obsidian annotation scripts and rules: Automatically capture and annotate items (to use with Obsidian)