Thought I’d add my data point here to counterbalance some of the amazing gains here 
I picked up TrainerRoad at the beginning of Covid in April of 2020. I saw some great gains – from 2.9W/kg to 3.8ish W/kg in about 5 months. I burnt myself out a bit and picked it back up at the beginning of 2021.
Started back over at around 3.2W/kg and plateaued a bit at 3.6W/kg.
Then I started a new job and then started prepping for a new baby on the way! 
I basically stopped all training for the better part of 10 months.
I just took a ramp test and … oof. My FTP is the lowest I’ve seen in years. Not only that, my W/kg dropped by even more since I added some pounds to my #dadbod. I’m now starting from a 2.67W/kg.
I’m hoping to get back training and hopefully fitness comes back to me. Also, this thread was helpful for new parents: Training as a parent