I don't see any general benefit of a classic analog scope over a DSO. There are of course specific benefits of specific devices, so for example you have Tek 7000 series with their boatloads of different amplifiers, including very sensitive ones etc. that might be more useful than a DSO with 2 mV/DIV — if you need it (see below) — and still cheap.
Or, for example, the great majority of DSOs - and all faster ones - have a fan which can be annoying to various degrees. So it might be an option to buy a cheap CRO to have something to work with if the fan annoys you again, or if you don't want the fan to make noise because you want to hear something (like inductor noise of switching regulators and stuff like that).
Also (as I keep saying
old DSO tech is
old - it's pretty shitty compared with even the cheapest Rigol or Hantek scope, all of which have larger memories and much greater single shot bandwidth. Only the very high end DSOs from the 90s can still compete with cheap and midrange DSOs of today.
Should I start working on a gear collection like Dave's or just keep working with the Kikusui.
Well, honestly, if you want to actually
do electronics stuff I'd advocate against trying to collect random gear just because it appeared in the background of some video of some guy on some video site - this still holds true if some guy is Dave. Instead, think about what kind of gear
you can put to good use - what is useful to
you? Knowing that is much more important than seeing something in a video and thinking you can't build electronics stuff of kind X without that thing.
There are some things that are common to electronics tinkerers, like a multimeter or a scope – but I really wouldn't prescribe any specific kind of either. Buy what is useful to you with the money you would like to spend ; everything else will probably just collect dust on some shelf in your home.
Usually, if you need something, you'll know it, although there are exceptions, as to every rule there are, so you might need/want something without knowing that yet.