I think you should feel free to rant to release some stress, but no the system is not entirely in the hands of one person with no balances and checks.
There are reviews of recommendation by staff, audits, requests for more information, collecting evidence and finally appeals. There are plethora of court cases that both validated or went against IRCC's decision. However make no mistake, there are laws and rules in place for this specific area of the spousal sponsorship.
For example,
Bad faith
4. (1) For the purposes of these Regulations, a foreign national shall not be considered a spouse, a common law partner or a conjugal partner of a person if the marriage, common-law partnership or conjugal partnership
(a) was entered into primarily for the purpose of acquiring any status or privilege under the Act; and
(b) is not genuine.
Many court cases have reviewed and continue to do so, the requirements in determining both of those. Even a married couple does not necessarily meets the criteria as the two bolded criteria above are also requirements. Cases have determined that this determination must be based on evidence and therefore the two criteria above tend to be linked (i.e. proving one supports the other) but it does add some distinction nonetheless. For example a marriage that is now genuine will not mean that the applicant qualify if it can be proven that the marriage was initially entered with the primary purpose of acquiring PR. This is not however just based on only the opinion of the officer processing the case, it has to be supported by strong evidence, most often objective evidence such as testimony from other parties as to the intent at the time. Lack of credibility is another strong evidence used my IRCC, for example when officers determine that evidence provided by applicants is not credible. The overall test however tends to consider multiple aspects such as the intent of the parties, the credibility of the parties, the immigration history and the genuineness of the marriage, one flag in one area tends to invite stronger scrutiny in other areas.
Overall the checks and balances tend to achieve balance of speed and accuracy for the immigration process.
There are requests for additional evidence, referral for reviews, interviews, appeal to IAD (where even more evidence can be provided).
