Re: final cut pro x
First, they certainly haven't gone backwards. But agreeably, some aspects have gone a little off center. So maybe it's gone far forward, but a little to the left. :) Remember, the app is only $300, and in 3 years there has never been an upgrade cost, and you can install it on all of your machines tied to that Apple acct.
I'll address some of your list.
An audio mixer will be a welcome addition someday. But the downside of a trackless environment is that there aren't any tracks for a mixer to address. The hope is that a roles-based mixer will be in the future. And fwiw logic X integrates with FCP X very well for any advanced mixing. Missing mixer aside, FCP X's audio capabilities and filters are much more advanced that FCP 7, especially in their individual interface components and real time abilities. You might not have noticed that you can actually edit the audio levels during playback, including levels, filters, keyframes, whatever. It just keeps on playing. In fact the waveforms will adjust on the fly to give you visual data on your levels as well. Other advances like sub-frame audio editing put FCP legacy to shame.
Output settings are created in Compressor, and FCP X has direct access to any of your compressor output settings. You can certainly create and share compressor settings easily.
OMF export should be available with an app called http://www.x2pro.net
Or, alternatively you could purchase Xto7 to convert FCPXML to XML and open your project in FCP 6 and export OMF from there. But FCP 6 is so old I'm not even sure that FCP 7 xml will work, but I think so.
That XML above might work with logic9 as well.
As far as why FCP X is better than 6/7 the list is huge. Native file format support especially. Transcoding isn't necessary unless you want to work with ProRes, and the app will handle that for you. It'll also create proxy versions that you can switch in and out of with a keystroke. It also natively supports 4k and has started moving into LUT support. Processing is better. RealTime is better. Titlling is better. Integration with Motion templates is amazing (send to motion still missing though) and the plug-in market is just off the charts. Head over to MotionVFX to see what you can do in 3D for next to nothing in FCP X. Or head over to CoreMelt to see their motion tracking plugs that are based on Mocha. Beyond that logging and media management is best in class. Nothing compares to the new multicam features. Look into auditions. Check out how libraries work to edit between projects. Check out the integration with Resolve. The scopes in X are the best software scopes I've seen in an NLE and then some. Yeah, a lot of stuff isn't right, but what NLE is perfect? Some things might be better in FCP legacy (like XML/OMF), but apps like xto7 and x2pro have filled that void easily. Sure they cost a few bucks, but the entry to FCP X is essentially nothing compared to other options. Perhaps X doesn't work for you. Premiere is excellent too, and it's only $600/year for the rest of your career.
In any case, I'd suggest you move on from FCP 6. It's at least 7 years old. It might interface with other old apps like logic 9, but if you're looking for something to work on the next OS, I'm guessing it won't. And with 4k the next norm, it won't handle it either. You don't need to move to X, but yikes, you can't stay there unless you want to lock your system into whatever OS is working for you and never update your hardware again. Time to move forward. X will suit your needs. But you've waited so long to update your software across the board that any change is going to be more and more of a struggle and learning curve the longer you wait.