Not a perfect solution as it adds more moving parts, external device hosting Node-RED, which can be from as simple as an android device to a RPi to a home server, but it is rock solid from my experience and you get a lot of control.
The nodes mentioned in that post should work, they hinge on determining the room via the serial number of the echo device that got the wake word and request, but supposedly there is a new maintainer so you may want to check them out first.
For instance I use these to do room aware goodnight and good morning routines, lights on/off, motion sensors on/off, thermostats on/off, fans on/off, along with just more robust routine control in general. Those nodes are super powerful and if you need any examples just give me a holler or post in one of those threads.
Not defending their sluggishness as I agree with you, but to be devil's advocate, imo they are leagues ahead of the competition, Apple and Google and even IFTTT in most cases (especially with price now) , in terms of smart home integration and automation robustness that they can get away with it. That being said I agree with you and make sure to send them feedback so they know what we want.
How well does that work for you btw? The reason I went down the NR rabbit hole initially was because this feature was broken beyond belief and Amazon support was convinced that the feature didn't even exist. It routinely controlled both lights AND plugs in a given group even though the plugs were categorized as plugs and NOT lights.
BTW, credit where credit is due, this is the original thread I based my design on:
OH, there also is another way that is a lot more hacky and has a lot more latency but is self contained on the hub that involves Echo Speaks and the wasLastSpokenTo (I think that is what it is called?) attribute, but I would not recommend it.
Here is an example:
