People who "just wanna play games" probably won't be using MESS anyway.
People who just want to play games are useful for testing and ensuring the emulator works well. They need to be a consideration, and need things to be easy.
There's no reason that a few years down the line MESS won't be the first choice for many systems, and the 'all under one roof' aspect is handy. MAME might not be the best emulator for all the systems it emulates at any given time, but it gets used because it's relatively easy to use, and convenient once you realise it needs specific romsets etc. Console users might not be used to this yet, but anybody familiar with MAME will be able to pick up the concept pretty quickly.
The target for all these changes should be to make MESS the 'MAME' of other systems. MAME already has a large user-base, and keeping things working in a similar way to MAME means that people familiar with MAME can support MESS users more easily, and are more likely to use MESS themselves due to the level of familiarity. As the emulation of the various systems improves it will become more and more accepted as a good way to play the games as well as a monumental achievement in the proper documentation of the systems.
For this to happen the entry point for usage needs to be as close to MAME as possible for this to happen IMHO, and it needs to be more obvious that this is MAME, but for consoles and computers. After a while people will pick up the more advanced techniques as long as they have something they can relate to in the first place, otherwise they'll just give up.
As for rants against the Good tools? well yeah, I think everybody is aware of the problems with the current lists and databases and hopefully MESS will provide an open platform for doing things in a more organized, detailed, correct and maintainable way. The 'Good' tools served people well for a long time, and while you can easily argue that they built up a mentality of collecting bad dumps etc. and even have some known bad dumps marked as verified good they did provide some method of organization and ensured that a number of dumps weren't just lost forever. Can you imagine if the 'good' project had been started by somebody who only cared about listing the latest revisions of games instead, or something equally horrific? We'd be in far more of a mess than we are now
Believe me, there are people out there who would do that, NeoRageX development was all about hacking the roms work with the emulator, and declaring those roms good, so the good tools weren't *all* bad.
So.. they served a purpose, but moving forward things can be done in a better way, I don't think anything more needs to be said about it. Evolution happens, and I think people are over the OMG I can play MegaDrive games on my PC stage and ready to start doing things the proper way ;-)
As an aside, I'm still concerned that there aren't good methods to dump some CD formats yet, That CDi-Ready stuff sounds curious, because by the sounds if it the data track is actually an 'audio' track (the data is contained in the pregap of an audio track, like some hidden 'rewind to play' tracks on some audio cds?) Tosec don't even know how to document these properly, and the only rips that work are ones where they've been hacked to report the first track as a data track. It's a problem that's nagging me a bit, and hopefully one that MESS/CHD format can solve so that others can reference it and use properly dumped data that actually works.
Final note, was it intentional with the various recent MESS->MAME code-porting that the throttle key is no longer mapped by default? This seems a slightly odd decision as it's handy to have, but I remember it not being mapped in MESS either, it was one of those nagging inconsistencies.