I like this tag thing if I'm searching. However, if I want to review and get a larger picture of the work that needs to be done per project, there needs to be categories of tasks per project, often called tasklists. Tasklists aren't present in Gantt, they are just a way to organize your tasks. Typically you have someone assigned to all tasks within a tasklist(actegory), but not necessarily the tasklist(category) itself. It's just a way to organize the overview of tasks.
For example, if your launching a company, then the project is the company. Then, within that company project, you to be able to categorize(tasklist) your work, such as operations, marketing, accounting, website/web-apps, etc, etc. Without categories(tasklists), you cannot get a overview. Sure I can narrow it down if I know what i'm looking for through tags, but what if I don't know what I'm looking for, or want to see which area(category) needs help due to the number of open tasks?
Currently, my work around is having these really long titles to task names(company-category-area-task). Even then, I don't know what I'm looking at half of the time because projects aren't listed in alphabetical order and are mixed up. It's a mess and I cannot keep it organized.