I'd say he was better than Alonso that year simply because he came in as a rookie against the reigning 2x WDC and finished ahead in the standings.
Rosberg being the unlucky one in 2014 is a bit of a hot take
, if I remember correctly Hamilton had horrendous reliability issues at the start of the season and had to climb back from multiple large points deficits.
So what if Bottas is inferior, who's to say that Rosberg if he'd stayed would have been able to take one or more of those WDCs (more likely Vet as Ros/Ham would've taken lots of points from each other)? It took a healthy rub of the green for him to win one at all, and if a driver of his talent couldn't handle the pressure competing with LH put on him why do you think it matters that Bottas is a step down?
You haven't actually put forward any reason that LH shouldn't be in the conversation for goat, you just seem annoyed that he had an easy ride against a worse teammate for a few years. Even in those years he twice had a serious challenge from Ferrari before they imploded towards the end of the year. I dread to think what your opinion of certain other multiple WCDs must be if having a worse teammate and good car automatically DQs them from greatness.