For people new to the DIY skills it requires to do it right, 2 months seems reasonable. You have to learn the skills, and when you're applying them you stop constantly to check tutorials or look for advice. You take the entire project one step at a time and you do one part before even starting to research the next.

A day of demo leaves you with an empty room with pipes sticking out of the walls. Maybe you've removed the drywall too so now you have outlet boxes and studs to work with. You take the rest of the day to finish the cleanup and triple-check your measurements for everything. Half your weekend has now been taken to demolish and clean up a core part of your home.

The next day you do your framing, including buying your lumber. Again, if you're new to this, you're probably checking a tutorial or plans every 10 minutes as you go so you make sure you're doing it right. If you have time and you're confident, you can get the plumbing set up so that it's ready to drop the tub/shower and vanity in place next weekend.

For someone with experience, this is an excruciatingly slow pace. For someone who is doing it for the first time and may never do it again, this is pretty reasonable. I would absolutely be proud of taking two months to do a bathroom if it means it's done right the first time. Going by the comments about contractors here, that's not a guarantee just because someone else can do it faster.