There was no such thing as a controller or a DJ having all their music on a HD or loaded on their computer. Active speakers weren't the thing that I know of in 2000 when I came back.
I think I got introduced to MP3 in
1998. By then the patents were being fully enforced and new applications were emerging from the technology. I saw the writing on the wall in 1985 (LaserDisc) while I was still 100% vinyl and knew big changes would be coming. By 1998 a neighbor of mine working in IT who also worked for me as a DJ showed me a 20
MB hard drive filled with thousands of songs in MP3 format, The capacity of the drive (and note that it is 'Mega' not 'Giga') almost exceeded my mobile CD collections and occupied 1/600th of the space. I was fully CD by that time with 5 mobile systems. Seeing what musicians were doing in studio with McIntosh and live with MIDI was truly eye opening as well.
There were a lot of new intermediate products along the way, but the DJ sector is a small ancillary market, so it took a long time before reliable memory buffers and instant start in CD players made it to market. I decided to stay predominantly CD until all those same kinks and PC stability for DJ applications caught up. It was a very long road from Vinyl to the fully emulating and threading PC applications available today.
I was fortunate to have imagined in 1985 some kind of higher-tech future while examining all the curious capability in LaserDiscs. I thought to myself that if this LaserdDisc could contain 5 languages, and 3 alternate endings for the movie - then why couldn't all the data I use (BPM, Key, Intro, Outro, Pitch, Tempo, etc) also be stored on a disc and interpreted by some smart mixing disc player? Today it's a multi-functional computer rather than a dedicated player - but, even without AI it was clear by the 1980's that "mobile DJ" was not a guaranteed future.
To some extent, there's benefit having had to self-learn the technology at the same time that it was still developing. I bought my very first "state of the art" personal computer in 1987 - IBM compatible, DOS, with 20MB hard drive, 3.5" 720Kb floppy disc, 15" Monochrome monitor, & Dot Matrix printer, at a price of about $5,000.00 (36 equal monthly payments on my Amex card.) It was a business machine (nothing music related) and it was then that this field solidified for me as a business which needed to be operated as such.
Adjusted for inflation $5,000 in 1987 would be an investment of $23,800 today, and that purchase was simply for a piece of office equipment. It illustrates that even at this very modest level, any business no matter how small requires some meaningful investment. Thankfully, technology gets cheaper as manufacturing processes improve and innovation advances. The point is - that to succeed at anything you have to be able to speculate on a realistic future (or lack thereof) for whatever it is you are doing. For me, that first PC gave me indexing, information, and documents capabilities that moved my DJ work into a much more serious business sphere, and made me focus on skills that would survive the technology rather than getting bogged down in the "bling" that so quickly changes.