Its a compromise.
Using this is far better then using the same exact password for everything or a weak password.
On the other hand it is all your eggs in one basket so if lastpass is compromised, EVERYTHING is now compromised.
I personally dont use it but for people who are just incapabile of using good password policies I recommend it to them.
My advice to people is start with a base password, and then add to it bassed on the tier category
Tier 1) site forums (like this one) no data lost, no money lost if compromised - base password (8+ characters with numbers and letters best if not be just one word)
Tier 2) social media - assume password is comprmised the second you type it in - shoudl be completley different from other passwords
Tier 3) Email, cloud storage, personal accounts - these have personal data in them so add a prefix or suffix to it
Tier 4) utilties websites, ecommerce sites, etc - these have your your credit card info so add something more to this password
Tier 5) banking - driect access to your money - you should have base pasword plus prefex/suffix, upercase letters, adn characters.
If you follow that tier list and make your prefix suffix in some way releavant then it is not that hard to remember most all of your passwords.