I mentioned the exact thing in last year's Picard thread. Patrick Stewart's voice has always been his main power as an actor. So much of his characters' authority is transmitted through his speech, which is why he can be as commanding in a wheelchair as he is on a starship.
Sadly, Stewart's voice has lost a lot of its strength and resonance, and with it, that amazing air of authority. Hate to say it, but you're probably right... Jean-Luc Picard doesn't work with a shaky weakened voice.
Interestingly, William Shatner is a decade older than Stewart, yet his voice is still robust, if darker.