My experiences are different (slightly). I played bass all through college into my 20s and early 30s. I then started working with a songwriter who did drum programming, guitar, singing and piano. Naturally I wanted to raise my game so I started playing acoustic guitar quickly followed by mandolin then before I knew it I was on harmonica, banjo, lead guitar and dobro. The reality was I wasn't particularly good listening back now and spread myself far too thinly. Worried I always sounded like a bassist playing other instruments I focused on just guitar and went for lessons. My guitar playing just skyrocketed! The other instruments got left behind but a couple of years later when I started picking things up I was suddenly much, much better on all of the things I'd forgotten about.
If you are starting, focus on one thing and build up your skills a little bit before branching out. Most multi instrumentalists tend to be "jack of all trades, master of none" which is fine but get the basics down a bit on one first and you'll benefit longer term. I'm pushing 40 and still very much learning on everything now. Have fun along the way