Generalist usually requires a moderately high skill in lots of fields, characters, environments, compositing, rendering, lighting, etc… This usually takes quite some time but you will find most archviz people are basically generalists with a specific focus on one area (vegetation, people integration, fabric, camera skills etc). This takes time, this takes a lot of practice and real world production skills (client interaction, photography/done matching etc).
My advice is if you wish to be a generalist at this stage, you should master each skill and demonstrate it specifically. For example, if I were to give advise to myself 10 years ago I would say, do a good camera match with 1 chair, light the chair really damn good, give it some fur or realistic type material (check bertrant benoit for an example of a simple chair - which is not so simple.) integrate it with the camera/environment so it looks flawless.
Then move on to a plant, find out the qualities that make a plant look realistic, the SSS involved in leaves, the different types of genus, you will quickly see how much plants vary from other plants and how intricate the modelling, texturing and ‘growing’ required for this type of work is.
Characters/Humans, this is an entire field of its own, I would advise as a generalist you pick a path for your first 5 years, either environments or characters - whichever takes your interest. These are very different beasts. Characters require… ‘character’, topology, sub-d workflow, in most cases PBR workflow, anatomy, the list goes on. Im not a character artist so Im not entirely qualified to give you more information you would really have to study this field - or ask artists here who are skilled in this area - but I assure you its another 5 years minimum, in fact I would say more if you dont have a formal art background or a knack for this field.
Once you know where you want to start thats the best place to be, then find artists you really appreciate and copy their style of work, eventually you will get to their level (yes, it might be 2-3 years and you are behind but that doesnt matter, the value of what you learn will be worth it later as you excel). As Jordan Pearson says “its amazing how efficient, efficient people can be, its off the charts how efficient they are…”.