No. The House of the Dead, Company of Heroes, Super Monkey Ball and Total War are seriously significantly big franchises, especially for their genres. This is also ignoring the fact that they avoided using other well known SEGA IP too and mostly just went with stuff the developers seemed to like. Imagine trying to argue this against non-Super Mario IPs in Smash Brothers. Star Fox and F-Zero barely sell so might as well not rep those!
Also Sonic Mania is easily the most beloved Sonic game since like Sonic Adventure both externally and internally, do not try to pretend it is some small game brushed under a rug. Especially with all of the animated shorts, merchandising and all of the times it has been listed as an especially important release in the franchise. It is also not digital only either.
I do not think having new releases in some of these franchises is relevant to crossovers (though I would prefer they pick more constant franchises than stuff like Billy Hatcher) and I am not trying to act as if including titles like Space Channel 5 (which does have a new game on the way) somehow immediately makes this a better product.
What bothers me is that some people present that this is a much better focus for marketing purposes. They openly ignore that characters like Omega, Zavok and honestly probably more than half of the cast in this game are much smaller time characters than just about anyone significant you can pick from another fan favorite game franchise. In the end past games already had the most popular Sonic characters anyways, so I am not sure why so many act as if this is a gamechanger.
I am personally not too terribly disappointed with it being Sonic exclusively. I just wish if they were doing something like that they did more deep cuts. Sand Hill Zone from Sonic Adventure certainly caught me off guard though.