Len doesn't plan trips for people. He gives tools for people to plan their own trips. I've used his tools quite successfully in the past and will continue to in the future as I've found value in them. If you don't that's fine, but I've found them helpful.
Exactly. TP provides some very useful tools backed by historical data and statistical wizardry. It's up to you to use these tools and any other information at your disposal to plan your vacation. I'm a TP subscriber and have found their information quite valuable, even if the crowd estimates miss from time to time. This is information that isn't freely available elsewhere (yes, there are some other free crowd calendars, but given Len's background, I trust TP numbers more than anyone else).
And, to be clear, this is different than an authorized Disney travel planner. Disney travel planners do help plan vacations for you. (The keyword is "help"...you can still do as much or as little of your own planning as you like.) Disney travel planners get paid commission from Disney and do not cost you any more than it would cost if you did the trip for yourself. The benefit of using them is that they have experience that some Disney travelers do not have and also are willing to get up early to help arrange FP+, ADRs, and apply discounts as they become available. And they've got your back if you need help with some of the stickier vacation planning situations. But again, their services are free to the traveler...if anyone is charging you a fee to plan your travel, then you should probably look elsewhere.
Given that their services are free and they will still allow you to do as much or as little planning as you'd like, it's hard to see any reason why most travelers wouldn't use a Disney vacation planner. Certainly, their services are most valuable to Disney newbies, but even the seasoned Disney traveler could benefit from a little free help.
(Full disclosure, I know these details because my wife is one of those Disney vacation planners. Not an advertisement...just disclosing my interest in the subject.)