Just a cost analysis regarding the price for ad-free and what you actually get from ads. I can only use myself as an example, so that's what I'll do.
I visit the site three times a week, I check the results of my game, gameplan, and then check league forums, which aren't very active. I usually spend less than 5 minutes on the site at a time.
You get what, $10 CPM on the ads? If I'm visiting the site 125 times a year, it's going to take you 8 years to make $10 off me. But you want me to pay $30 a year? If you get $1 a month off me that's a lot more money than you would be making from ads. And far more people are going to be interested in a $1 a month cost than $2.50 a month.
When I bought credits I viewed it as donating, but with a subscription I view it as paying. Once I'm paying for something it becomes a matter of value. This is the way it works in people's minds. By doing this you have changed the way a lot of people view your service, and the value proposition has just dropped off a cliff.
It has been mentioned elsewhere but bears repeating: what are people paying for? There's no proof that you will continue to improve the service, I've been playing for a year and a half and the only update has been removing a single play.
A major concern for everyone;
What if the money you get from all of this is not enough to justify you working on it more? Knowing that it might not mean any changes to MFN, I'm very reluctant to spend my money to support the site. I'm very apprehensive to spend money now. You really should have waited until you at least released a new update before considering a change like this. People have absolutely no confidence that you will make real updates to the site and the engine because your track record isn't great. And now you say you need more money to justify working on it, and everyone here realizes that most people aren't going to want to pay in the first place, which just compounds the idea that you aren't going to be getting enough money to warrant updates, which makes everyone wonder what they're going to be paying for - they're going to believe that to be nothing. That strongly discourages the people who want to support you from supporting you.
I want to support you, but I can't justify it. I don't customize my team often, I'll have my admin do it. I'll use an adblocker because $30 a year for ads is astronomical. I only play in my one league as most of my league does (we make up about 10% of your player base btw) so the free tier is fine for me. A UI update will be welcomed, especially for mobile, but that's not a real update to the game. You need to make paying worth it. Add more features for a paying customer, and stop paywalling existing features.