Thing number one you can do - and this generally beneficial, but it's especially beneficial in this sort of family dynamic - is just do what you can to simplify. And that can mean simplifying the portfolio in terms of fewer total holdings; a slice-and-dice portfolio with small-cap value funds and international small value funds and a REIT fund and all these different things that you might see: maybe that's pretty neat to you and maybe you think that's going to give you some slightly better risk-adjusted return. But, if you know your spouse isn't interested in this, it's not helpful to them.
A simple three-fund portfolio - or in some cases, just a target-date fund or a life strategy fund (although of course those are not good fits for taxable accounts). Simplify now, rather than expecting your spouse to do it on their own later.
And additional point there: cognitive decline is a reality that happens to most people, to one degree or another. We don't know exactly when it's gonna start or how quickly it's going to happen, but same thing there: the simpler the portfolio is, the better the position you put yourself in.