You are right. Even for educated folks, the level of English comprehension/diction in Bangladesh is quite poor.
As a result, a khatash (smelly civet) like me has become a ladykiller tiger locally in Dhaka. I am the life of Iftaar parties.
English starts shooting out of my mouth - I start attracting crowds....
Key to speaking English well is to speak it often with others who have decent proficiency..
I used to speak like the average Indian expat until a couple years ago.. when I started played online games, I would spend atleast 6 hours or 7 hours in voice chat with Englishmen..
It hit me that speaking English merely isn't enough, communication is about getting your message across to the other party and if you can't speak English in a manner that is legible to them then it's as if you don't know English at all. This is the case with Bangladeshis who claim to 'speak' English.
Anyway , I just listened to how they speak (the Englishmen) and tried to replicate it..
It's not just how they enunciate their syllables.. it's also their sentence structure..
The sentence structure taught to me by Indian schools was so... Simplistic.. it lacked any flavour whatsoever, like speaking English for the sake of it.
I guess what I'm trying to say is.. if you want to master a language, listen to native speakers speak.
That brings me back to my point, BD kids couldn't give a flying **** about fixing their English they're busy singing Teri meri and so on...
I can read and write Hindi, when I revealed this info to my relatively young cousins they thought I was a God and all of them wanted to hear me speak it..
I ask... Why this thirst for Hindi but not for English ? The world wonders