It's not a good idea if you have very little money and can't risk making a mistake. Most ICOs are and will be scams. You can calculate your chances in many different ways it can be 30 to 70 or 20 to 80 but in the end you will be at a disadvantage. If you have a lot of money already invested in Bitcoin you can always put 10% of it into ICOs.
Well, it is a normal thing to back away from something as a person, most especially when the condition is not favorable for investment and that is how I basically feel most investors are thinking right now when it comes to investing in ICOs. Certainly 2018 was like the worst year for most ICOs, but it is what it is. However, it is interesting to note that a lot of investors are becoming wiser these days while making sure they consider what they are investing in first before investing in it, unlike before.