"What does "Rigol DS1054Z is the best oscilloscope for hobbyists" mean?"
It means that it is the purchase with the best price/feature ratio for hobbyists, with the main reason being that hobbyists can unlock ALL cost-options for free, without any legal consequence. This might not be the case for companies or schools.
A hobbyist uses the oscilloscope (or any other equipment) for personal projects, which are not profit driven. Mostly the hobbyist does not gain any profit at all with his activities, hence why it is not reasonable/affordable to use expensive equipment designed for high end professional use.
That does not mean that there aren't hobbyists with high end equipment.
BUT: The fact that this is the best buy for hobbyists, doesn't disqualify the oscilloscope for professional profit driven applications!
The question is: what are you using it for?
Example: an engineer implementing CMM machines, CNC machines or robot cells, may use the DS1054Z at his advantage for example on motor/encoder calibration. Actually, any oscilloscope might do the job, because you are basically tuning motors/encoders, so that the waveform is shaped as close as possible against specification. Having the DS1054Z is probably a luxury compared to an old CRT analog scope.
Also, if said engineer needs to figure out the RS232 parameters on an undocumented CNC controller, in order to do DNC: sure, one can systematically try all combinations (300, 600, 900, 1200, 2400, 4800, 9600, 19200, 38400, 56600, ... baud, 7 or 8 stop bit, even or par, 1 or 2 data bit - yes, I have done it like this in the past, it takes hours), but with the DS1054Z, you can actually SEE the RS232 communication and deduce the parameters in a few minutes (I know you can use a logic analyser, a RS232 sniffer or a PC with two serial ports and sniffer software, too).
In these examples, you could do the same with a 10x more expensive scope. Higher specs, better precision, better GUI, etc. But in the end of the day, the DS1054Z would give you more profit.
If, however, you are into some kind of electronics repair or development, the DS1054Z might be less productive, offer too little bandwidth, to small sample memory, to little precision... All this has been explained on the several threads.
The only thing I really want to add on this discussion, is the value on academic articles (I lecture at university, also).
If a paper is discussing results based on MEASUREMENTS then yes, the equipment used to obtain said measurements needs to withstand any questioning: it has to be done within manufacturer's specs, with traceable calibration. Using equipment from a reputable brand helps.
If the paper is discussing a proceedure or technique, which requires a given instrument, then I find it absolutely acceptable to use the most competitvely priced equipment, as long as the choice is correctly justified. If the OP is using the oscilloscope to show how to calibrate the robot's encoders to increase overall positioning precision of the robot and if the oscilloscope is used to tune the accelaration curves of the motors, which are magnitudes under the specified capabilities of the oscilloscope, then there is nothing wrong in using a Rigol for the job. Especially if the OP explains the benefit of said device in the paper by discussing price/benefit ratio.
The use of expensive equipement per se does not justify anything and does not make a paper more credible. The opposite is the case: if too expensive equipment is used for no apparent reason and without any justification, then it gives a bad note to the paper.
My opinion is: if it takes the OP so long and so many questions/threads to make up his mind, then it seems he doesn't really need the oscilloscope at all!
If he knows what he needs the oscilloscope for, then he just needs to compare his requirements against the oscilloscope' specs.
All the rest has been said and discussed at length.
Regards,
Vitor