Used Coinomi in the past for some altcoin storage and never had any issues with them personally, probably they have bugs but, Do they really have vulnerabilities?
Coinomi had a really severe vulnerability where they sent the mnemonic code to the google server to check the spelling of the words.
While mistakes can happen, the developer claimed that this isn't as sever since google employees stealing funds would be unlikely. They completely ignored any other attack surface coming from that vulnerability.
The really important thing is not that the vulnerability existed, but the missing competence from the developer to acknowledge it. There are better wallets with more competent developers available.
Then how these wallets are considered as best crypto wallets for everyone even in 2020?
There is no central authority who gives out a prize for the "best wallet".
People might choose them as the best wallets for random reasons (e.g. good UI and easy to use), they don't necessary have the technical knowledge to question it form a technical perspective.