Yes, maltodextrin is not sweet enough. I don’t know what the exact comparison is, but if you look at the ingredients of any sugar substitute packet, you will see that the actual artificial sweetener is cut with maltodextrin. This is because the amount of things like sucralose or aspartame required to get the same sweetness as a teaspoon of sugar is absolutely tiny. It is so small, that people would have a hard time getting it out of the packet. So they cut it with enough maltodextrin to get closer to that teaspoon. Now, consider this: If maltrodextrin had significant sweetness, why not just put only that in the packet? I have not actually tasted pure maltodextrin, but I was under the impression that it is barely sweet at all.
As far as the glucose question goes, most of the answers are right, but a few things were missed. The biggest reason to avoid glucose is precisely that it is the primary sugar used in the body (note, however, that the body can also derive energy from fructose and from ketones generated when fat and protein is broken down for energy). The human body is not designed to consume glucose directly. (Ignore the “it’s a chemical” arguments. Even water is a pure chemical. Everything is chemicals. If you want to avoid chemicals, you are going to have to stop eating, breathing, and drinking anything. What matters is how chemicals interact with the body, not the label.) The human body is designed to consume things that can be slowly converted into glucose by the body. The worst case that does not have significant potential for harm is consuming carbs and sugars that take a long time to break down and convert into glucose. This provides an inherent level of regulation, preventing dangerous blood sugar spikes. Ideally, blood sugar will barely increase at all after consuming food, remaining close to the same low level constantly. When this happens, the body can regulate sugar uptake into cells very efficiently using insulin. The best case is to consume foods that the body can easily regulate entirely on its own. This is mostly limited to fats, though limited amounts of protein can be regulated easily as well. Fats take a long time to break down, but more importantly, the body has nearly complete control of the conversion from fat to glucose, which allows it to keep blood sugar extremely stable. The reason stable blood sugar is so important is that our insulin mechanism was not designed to control blood sugar. It was designed to control uptake of sugar from the blood into cells. The liver is designed to control blood sugar (and other things that might be in the blood). It uses insulin as an indicator for when blood sugar is high, and that is when it starts converting it into fat and storing it. When insulin is used to control blood sugar, the body’s cells start changing how they respond to it. At first, they get hyper responsive. They start taking up more glucose from the blood than they originally did for a given amount of insulin. This is a sort of “stock up in times of plenty” kind of mechanism, and when it gets severe it leads to hypoglycemia (constantly low blood sugar, because the cells are quickly taking it all when any insulin is released). This does not last forever though. When there is always plenty, eventually the cells will stop trying to take advantage of it. In fact, too much sugar in the cells over long periods of time can be a bad thing, so eventually they become hypo responsive to insulin. In other words, for the same amount of insulin, they absorb less sugar than they originally did (this is called insulin resistance). This leads to constantly high blood sugar, otherwise known as type 2 diabetes. The body tries to compensate by releasing more insulin, but at this point, the liver is the only organ responding fully, and when it sees insulin, it starts storing sugar as fat. And this is why diabetics tend to be overweight.
Artificial sweeteners are complicated. It turns out that while they don’t increase blood sugar, they do invoke an insulin response as if they had. This can be a factor in getting diabetes, but it is not as bad as things that cause real spikes in blood sugar, like glucose. This needs more study, because we don’t actually fully understand what happens when there is an insulin response when blood sugar is not high, but it is probably bad. The question is whether or not it is as bad as just eating the sugar would have been. Also the mechanic is important. If the sweet flavor is the main mechanic, that has different implications than if the body is just mistaking the molecules of artificial sweetener as real sugar.
There is one other issue with glucose: Because it causes a very sudden increase in blood sugar, it has unusual affects on some people. My wife gets headaches when consuming pure glucose (doctors like to use a glucose drink to raise blood sugar to test for risk of diabetes during pregnancy). Many people get lightheaded and dizzy from it. In very small amounts, it probably won’t affect most people, but even if it affected only 1%, that is a pretty serious set of side effects. Imagine drinking a bottle of Soylent while driving to work and getting lightheaded while driving. And keep in mind that sucralose is way sweeter than glucose. It would take a lot of glucose to get the same level of sweetness.
Anyhow, that is a more complete answer, at least when it comes to the affect of the chemicals on the body. If you want to learn a bit more about the blood sugar stuff, especially in relation to the difference between carb, protein, and fat metabolism, check out this TED talk: https://www.youtube.com/watch?v=da1vvigy5tQ.