We're not a hybrid of LXDE and Xfce (no matter what the press suggest) we simply cherry pick the best components no matter where they come from then incorporate them into a cohesive whole with our own software. If you think about it very few distros use a full DE including ALL its components , most swap out peripheral components such as using gedit instead of leafpad/mousepad, and/or choosing a more functional terminal emulator over the stock one, etc. Peppermint was from the very beginning following such a path and replacing components where better ones were available that didn't impact performance but added functionality.
In our opinion no DE is perfect .. for example, LXDE's session management is lighter and more modular than Xfce's, but the Xfce panel is more functional and has MANY more plugins than the LXDE panel/menu, Cinnamons Nemo file manager hands down beats PCManFM/Thunar/and even the now stripped down Nautilus for functionality and plugin/script extensibility, the MATE Calculator is the only calculator that acts exactly the same way as the Windows/OSX/iOS/Android one (yet doesn't have client side decorations), sakura as well as being Gtk3 is more configurable than LXterminal .. I could go on...
We decided that the whole point of open source freedoms and the UNIX philosophy of KISS and "do one thing well" were specifically designed to encourage people to build new (and hopefully better) things by stringing together existing code, this being why Linux has historically had a very modular design, something that is often lost in todays all inclusive non-modular DE's. So (hopefully) we're simply following those long standing principles and creating something better than any stock DE without (as VinDSL says) reinventing the wheel.
After all, isn't that the whole point of Linux/FOSS and its freedoms
Short answer:-
We're not a hybrid of LXDE and Xfce .. we're a hybrid of the best bits of
ALL desktop environments, we see no point or need to stick with all components from any single DE where those components aren't the best for the job.