Free speech is not limited to the First Amendment of the USA. Article 19 of the International Covenant of Civil and Political Rights (ICCPR) and Article 19 of the Universal Declaration of Human Rights (UDHR) both mention the freedom of expression, which includes freedom of speech.
Article 19
1. Everyone shall have the right to hold opinions without interference.
2. Everyone shall have the right to freedom of expression; this right shall include freedom to seek, receive and impart information and ideas of all kinds, regardless of frontiers, either orally, in writing or in print, in the form of art, or through any other media of his choice.
3. The exercise of the rights provided for in paragraph 2 of this article carries with it special duties and responsibilities. It may therefore be subject to certain restrictions, but these shall only be such as are provided by law and are necessary:
(a) For respect of the rights or reputations of others;
(b) For the protection of national security or of public order (ordre public), or of public health or morals
(ICCPR, 1976)
However, it is important to keep in mind that the ICCPR is a binding document between "States under the Charter of the United Nations" (ICCPR, 1976) and does not address corporations. Furthermore, Article 19 points out that there valid restrictions of the freedom of expression. Generally, private organizations are granted more leeway in the restrictions they can place on various rights, including freedom of expression. That's why the HoI3 and HoI4 forums are able to state specific rules that you must follow to be allowed to post, including topics that must not be named.
Now, to address the OP's point about the maps and aesthetics. Let me point out that I haven't played HoI3. I have watched some let's plays and read a few AARs, but that isn't the same as playing. So I understand that I cannot really speak to the functionality of the HoI3 maps. But I can discuss the aesthetics of both the game and the maps.
First, I find calling the aesthetic cartoony is not really that helpful. Because the HoI3 colour aesthetic is also found in cartoons. Is calling it cartoony just a means of denigrating the aesthetic style because cartoons often carry with them the connotations of being for children? If so, then an entire artistic medium is being devalued just to voice not liking a certain visual aesthetic. And some cartoons can reach a level of realism depending on the art style, so having cartoony mean "not-realistic" doesn't always work.
Second, realism is worth touching upon. Actually, realism is a meaningful argument when discussing preferences. But it must be remembered that the nature of games places constraints on how realistic they can be. Furthermore, making the game fun to play might require toning down on some of the realism. And with WWII games that want to be sold in Germany, certain elements must be cut to make the game legal. These sorts of alterations are to be expected, but that doesn't mean you can't have realistic mechanics or at least approximations of reality. Now, is having giant counters move across a map any more realistic than having giant models animated on a map? I don't think so. Both are representations of military units. The Prussian Kriegsspiel used blocks of different sizes to indicate the type of unit and dates back to the early 1800s. H.G. Well's Little Wars (from 1913) uses toy soldiers and a toy gun/cannon that can shoot. None of these systems are fully realistic in terms of what they represent, though some might better reflect what militaries of the 1930s and 40s used for operational planning. For military planning, analysis, and running through possibilities realism in mechanics is essential as the goal is to find the strategies and tactics that will help your forces prevail and that goal cannot be met if the simulation does not match reality as close as possible. But for games, realism should not come at the expense of fun. Wargames are complex, as they should be. But this complexity should add fun and not frustration to the game. And when you analyze HoI3 and HoI4 they are really hybrids--part wargame and part grand strategy. You don't have to worry about building factories and assigning production in a game like OCS Korea--your units come according to the reinforcement table/chart. Instead you worry a lot about supply--are my units in trace supply, do I have enough supply to move and fire my artillery, do I have enough supply for attack and defense, can my units here escape being cut off, and such occupy a lot of your considerations.
Third, while there may be things off with the HoI4 map (like GB's and presumably Irelands geographical drift away from Europe), there are also things off about the HoI3 map. I'm looking at a screenshot from a Japanese AAR and am cringing at the creative use of Cyrillic for spelling out Mongolia and Tannu Tuva. The font type is not consistent as some nations (like Germany) get gothic lettering in HoI3. The font size on the historical map the OP provided shows variance (the British Isles, Turkey, and USSR have larger fonts than Germany, Spain, etc.), though not as much as either HoI3 or HoI4 (The Soviet Union's "S" is about 1/4 of Spain's north-south dimension in HoI3 in the image I measured). That and the colour scheme for shading nations on the historical map seems to match HoI4 more than it matches HoI3.
Fourth, the day-night cycle is present in HoI3. If you look at the mini-map you can see a day-night indicator. I have no idea if that has any impact on the game, but it is very clear that such a system exists within HoI3. So the decision to move the system onto the main map was probably made to make it easier to know when it was day and night. Not all who play Paradox games are super observant (some let's players are better than others...). And so I'm guessing that time of day will be important to know in HoI4.
Personally I think that both aesthetics have their strengths. It seems to me that the aesthetic of HoI3 more closely matches that of hex and counter wargames while the aesthetic of HoI4 more closely matches more popular strategy games. So this is likely part of an effort to broaden the appeal of the game. I would love to see a topographical (or close approximation) map mode, but I realise that the implementation would be a nightmare for the artists and could result in a lot of threads about inaccurate terrain depictions as topographic maps tend to carry with them a feeling of more authority than relief-style maps. I suppose there is always laying my topo maps out on a table and marching LEGO pieces, other miniatures, or self-made counters across them.
