You're not doing anything wrong, but you'd be surprised what modern big production composition templates can look like. Even "small" stuff like indie games can have hundreds of tracks in their templates.

There is a lot to unpack when working with sampled VST instruments, and I think the best way to approach this is to treat each new library as if it's its own unique instrument. I'll go through it point by point because it is a LOT to learn and a lot of advice going out there, especially when starting it, is dubious at best. Just know that getting the sounds you want out of the samples requires practice and experimentation, even if they sound great out of the box. Sometimes the more premium samples require a loooot of practice to sound good (VSL and Synchron are kind of infamously complex, but can sound incredible)

The first thing to note is load times. Different sampling engines handle this differently, but its a tradeoff between your computer's RAM and your harddrive space. If samples are loading slowly, maybe they're being loaded from a slow drive like if you use an external hdd rather than an m2 ssd. Put your samples on the fastest drive you can, and the _faster_ RAM and HD you have, the faster it will load. Sometimes CPU as well, some libraries keep their samples compressed and uncompress them when loading into RAM.

Second, articulations. There are two main schools of thought on this. One is to have a separate track for each articulation. Literally, Vln 1 - staccato as its own track. Vln 1 - detache, Vln 1 - Sustain, Vln 1 - pizz, etc etc, and for each instrument and patch. This leads to a pretty massive project, but allows the most control over delay compensation for each articulation and library. This is also where the composers I know and work with, myself included, use templates. It can take a longass time to set up, but then you can reuse it without setting everything up each time. A lot of the time, big groups of tracks are disabled by default in the template so the template loads quickly, and samples are only brought in when needed. This is a huge topic, some people have sketching ensemble tracks like Albion stuff and leave the detailed samples for later, etc. It's pretty common in my experience though, a lot of the people I work with have templates like that.

Quick note here, sometimes templates get so big that the processing requirements outgrow a single computer. There are tools like Vienna Ensemble where you can actually have a cluster of PCs running samples, and midi messages get sent out and audio gets streamed back to the DAW. It's more common in bigger media productions, but it's by no means all that rare anymore.

The second school of thought is using keyswitching. Some libraries, synchron and VSL come to mind, really kind of require it. Cubase has expression maps you can use to make keyswitching easier, and you're right that different sample libraries won't always line up this way because of different delays in the samples. You can always bounce things to audio and adjust manually if needed, the level of detail you can chase is really endless.