This is a cool website, and if people go past the landing page they'll find a trove of information and good descriptions of the initiative, as well as rebuttal of the criticisms I've read here so far.
For example, the website is a collaborative effort between multiple entities, and re: map details, they state clearly that "These maps are fluid and ever changing and should be used as an education tool to create dialogue around reconciliation."[0]
They also don't claim to show every single thing on the landing page. For example, living in Quebec, clicking on "Where Am I?" lands me on a list of nations which I'm sure is limited but is at least a starting point for discussion. They specifically mention "There are 634 First Nations in Canada. Learn more about those closest to your location", which might not be directly reflected on the landing page but is acknowledged on the website itself.
Their relationship to acknowledgement being part of a process of reconciliation is not a personal attack on anyone, and it saddens me to think that some people would take it as such. Their FAQ also brings forth the kinds of questions that one might come up with when being made aware of First Nations and treaties and such.[1]
For reference, I am European and I moved to Canada. Perhaps the emotional distance allows for curiosity and a wish to understand as main drivers, rather than feeling attacked or threatened in any way. And I'm French, so technically this is history that I should know at least partially! (but was never taught in school, as the kind of history classes I experienced were very focused on our own belly buttons - Pre-history -> Egyptians -> Greeks -> Romans -> Medieval Europe -> Monarchies (so much time..) -> Industrial Revolution in Europe -> World Wars -> Cold war).
Canada is making efforts towards a better understanding and acceptance of its past without shying away from saying things that temporarily would appear "ego-damaging". In my country, a bit over a decade ago the president was going to a summit of African countries to tell them how irrelevant they are[2]. The humility shown in this website (and to a larger degree in Canada, as evidenced by Trudeau's recent acknowledgement of systemic racism) is as politically challenging as it is morally right in the long run.
The past can't be undone, but the present can acknowledge and work to build understanding and respect for the paths taken.
[0] https://www.whose.land/en/about
[1] https://www.whose.land/en/faq
[2] https://en.wikipedia.org/wiki/Nicolas_Sarkozy_Dakar_address