I'm going to start by rejecting the three major premises of your question:
First, Your "personal freedom" in this case is already restricted by regulation.
Whether a penalty is assessed for each violation of this regulation does not remove or change restriction - You are prohibited from flying into clouds without an instrument rating, just as you're prohibited from throwing your empty soda can in the street because of laws against littering.
The fact that you might "get away with it" because penalties can't be enforced for every occurrence does not remove the fact that there is a legal restriction.
Second, inadvertent VFR into IMC is, by definition, an emergency - particularly if you are not an instrument-rated pilot.
Prudence already demands that a pilot in an emergency situation declare that emergency, and then use all available resources (including ATC assistance) to ensure a positive outcome.
A regulation saying "Pilots entering clouds without an instrument rating must contact ATC and declare an emergency" would be redundant, and ultimately you couldn't reasonably enforce it (you would have to prove that the pilot flew into clouds and did not declare the emergency your proposed regulation would require).
Third and finally, while some VFR-into-IMC incidents result in CFIT accidents the majority of these incidents that end in an accident do so because of a departure from controlled flight, and are classified as "Loss of Control" (LOC) accidents.
To the meat of your question: Would enforcing penalties against pilots who inadvertently fly VFR-into-IMC reduce the CFIT accident rate?
Judging by this ATSB report on CFIT incidents the Australians don't consider the penalties to be a significant factor: The words "penalty" and "fine" do not appear in the report at all, and if they were a significant factor in cutting the CFIT accident rate one would expect them to be featured prominently.
Based on the answer you linked to the enforcement of this penalty in Australia is discretionary:
The regulations (CAR 172) effectively states that if you fly into cloud the penalty is 50 penalty points - I think each penalty point is currently 110 dollars so the answer to your question is you could be fined $5500. However, CASA uses discretion as to when to enforce this fine…
The system in the US is similar: There is a penalty of up to $50,000 (for individuals) for violations of the FARs and you may also face suspension or revocation of your pilot certificate, but this is pursued at the discretion of the FAA, and is rarely enforced in cases of inadvertent VFR-into-IMC.
The reasoning behind this discretionary enforcement (and general lack of enforcement against inadvertent situations) is that we know pilots who get in contact with ATC and seek assistance are more likely to have a successful outcome.
Consistently enforcing penalties against pilots who inadvertently fly VFR-into-IMC provides a disincentive to seek that assistance: "If I tell them what happened they are going to fine me lots of money!" versus "If I tell them what happened they're going to get me safely back on the ground."
The primary responsibility of the various aviation authorities is to promote safety, and penalties are used as tools to facilitate that. Where a penalty would provide a disincentive to safer operation it is often not used, and alternate methods of enforcement employed (such as education on the dangers of VFR-into-IMC and incorporating risk-based decision making into training programs).