Donating reply:
The point of donating is to support the developer(s)/team who are putting their time and effort into a free product. It's like giving something back.
Filters reply:
Even with Free Ad-Blocking software, you don't have to be an expert to add/remove filters, the defaults work straight out of the box. However, should you wish to add more filters, the options are there and are clear to what they're offering (may differ between products). Not all filters are required.
Paid vs Free reply:
Personally, I don't see the point of spending $30 on Ad-Blocking software, may alternates are free and popularly used by both new and experienced PC people. Not every piece of software has to be paid-only. Imagine having to pay for Firefox and a subscription for using Google Search (Web and Image). What about Youtube becoming a pay-per-view site only?
You said, "Regarding the ABP, it's free perhaps, but I don't think that it would offer full features for free too."
What "full features" are you referring too? Because as far as I'm concerned if ABP blocks an Ad, that's job done.
So a paid product, does not equal a better product/service. (For example: Receiving bad customer support). Also there's a more than likely chance that 'The People of The Internet' will help for free products, so it's not a complete loss for free software.
Finally, you may want to disable AdGuard on MalwareTips as we
do not have Ads on the site. Value for money, right?