I think that if you take a larger view on the overall market, it's not that the home console market is shrinking because there are no big IPs on it. It might be the opposite. There are no longer many big IPs on consoles because consumers have started moving away from them. You mention stuff like Pokemon and Monster Hunter, but those were always big portable IPs. They were popular because they were portable, and not popular IPs which moved to portables.
Let me explain how I see it now. I think that "big IPs" will not really be able to push anything much on their own. It's not the branding, it's what people want to play. Appeal and demand make big IPs, not the other way round. Why are consoles less appealing and why is there less demand for them? Lack of software is certainly one reason, but it's not the largest reason. The reality is that games for the majority of people is not a dedicated hobby and just something they want to pass the time.
When the only option for a certain quality of gaming were consoles, they sold a ton. People wanted something to play, anything, and at that time the economy was strong enough to support the additional cost too. When portable gaming caught up and could offer experiences up to the standard the majority of people in Japan wanted, the market exploded to that instead. It was just more convenient and cheaper. They might not be "console level experiences" but clearly that wasn't what most people were after. Their standards are much lower. Now we're seeing the shift towards smartphones. Why? Because everyone has one and they would rather play games on something they already have than carry around another device and buy retail games.
This doesn't mean that dedicated gaming will disappear entirely, but rather that it will increasingly become the domain of enthusiasts rather than general audiences. Much like how the low and mid-range camera market was completely destroyed by camera phones, we're seeing something similar with gaming. In the end, the people who buy dedicated game hardware will demand higher and higher standards, while the number of them supporting the market steadily decrease. Smaller market, demand for higher standards. Tough times for everyone. So it's not surprising that many companies are choosing to go after mobile and portables instead, rather than fight tooth and nail on high quality console software in the Japanese domestic market.
I agree with many of this, but not everything. Portable success actually did cannibalize the home console market in Japan. Even though I agree some of the IPs were more successful due to portability as Monster Hunter and Animal Crossing, some IPs, once very identified with home consoles, migrated to portables.
Kingdom Hearts: From KH2 onward, we got seven games of the series, only 1 was for a home console and was a remake.
Dragon Quest: From DQ8 onward, all it's titles, remakes included, were portable titles, outside of DQ10 which was a MMO.
Super Mario: From Sunshine onward, 8 titles. 3 portables titles: NSMB, SM3DL and NSMB2 coming out first and NSMB Wii, SM3DW and NSMBU being heavily inspired from them.
Zelda: From Majora's Mask onward: 14 games, 9 of them portable.
Although some franchises remained consoles focused, like MGS, RE, Tales of and FF, they got major portable treatment as games like Peace Walker, Revelations, Hearts and Type-0 were big bets.
This, combined with everything you say, cannibalize the home console market as many of the major IPs once identified with it left it out or, in a way, had it's contribution for the portable market exodus.