A lot of old style people consider bpw to be tech only. I was flat out told that by a shop owner.
BPW is definitely not "tech-only." When I switched, I found it to be much more reliable, comfortable, and customizable for my needs. (I happened to switch to side-mount soon after, but I'm keeping my BPW setup).
Similar to long hose primary donation. This is just human nature, no different than the thousands of discussions about synthetic vs. non-synthetic motor oils for engine break-ins. Some people don't like change, some are unwilling to change. I'm happy to hear arguments against a BP/W setup for a newbie, so throw them at me. Right now I don't see how better/easier buoyancy control and weight distribution is a bad thing.
Long-hose donate tends to be an additional skill that is taught or can be learned from videos. It's not hard, but it is an additional skill, not covered in (most) Open Water classes.
An instructor may not have the time to teach long-hose donate in Open Water class, when the student isn't yet skilled in just donating a reg. I mean it's not hard, but it's just something extra, and it's just a little more complicated. In my Advanced Open Water class, my instructor looked at me funny at first because I had a long-hose. I showed him I knew how to use it and has practiced with it, but I wouldn't recommend bringing a long-hose to an Open Water class.
That's fair, but I prefer simplicity, common designs and fewer failure points wherever possible. I also love modularity, I like the idea of replacing just the parts that are worn or broken, rather than throwing away the entire product. That's why I'm gravitating towards the BP/W. The sidemount argument above was very valid, but if/when I go that route, I'd either keep the BP/W or resell it, so I don't see it as a big deal. Having spares/backups for myself or a buddy is never a bad thing either. When I go dirt biking (most weekends), I have a ton of spare parts with me because most of us ride bikes form the same manufacturer. I've been a ride saver on many occasions.
If you're future-proofing, I'd give a strong recommendation for backplate and wing. Now, there are different backplates, different wings, and different harnesses. I'd still recommend you don't buy a BCD (of any style) yet, because it'll give you time to do some research and ask questions. For example, I'd probably suggest a steel backplate, and a "small" wing. Large wings tend to create drag and make managing buoyancy a little more annoying. For the harness ... it depends on your preferences really. A lot of people go with the single-piece webbing setup, and it's fairly easy to learn how to assemble it. You can add or remove d-rings, or shoulder-padding, or customize it in a variety of ways.
That said, don't take my advice here and go out buying a wing, you'll want to start a topic asking for advice on backplate+wing setups. Preferably after you've finished Open Water.