That one feels kinda meh to me. It solves a handful of non-issues with our current calendar (I don't care that the month starts on the same day, nor do I care that each day of the year is always the same day of the week). Each months having the same number of days is an improvement. It persists the problem that you still can't use months or years as a real mathematical unit of measure and extends it to weeks, which is the biggest annoyance with calendars, although it reduces how often that becomes significant. Adding two days that have neither a day of the week nor month would mean significant changes to every computer system that needs to deal with dates, and is just hateful.

The 1st of a month to the 1st of the next will always be one month, but it depends on the month and year how many days that is. So a month as a duration will span either 28 or 29 days. A week is now sometimes 8 days, and a year might still have 365 or 366 days, depending on the year.
How do you even write the date for the days that don't fit? Like, a form with a box for the date needs to be able to handle Y-M-D formatting but also Y-YearDay. Probably people would just say 06-29 and 12-29, or 07-00 and 01-00, although if year day is the last day of the year it kinda gets weird to say the last day of the year is the zeroth day of the first month of the next year.

There's just a lot of momentum behind a 12 month year with every day being part of a month and week. Like, more than 6000 years. You start to run into weird issues where people's religion dictates that every seventh days is special which we've currently built into our calendar.

Without actually solving significant issues, it's just change for changes sake.