No you don't. I'm French, I dropped out of school at 16 and picked up English later in life without using any formal method of learning. I started by memorizing enough vocabulary to read simpler English, after which I began reading popular fiction and watched movies with subtitles (in English) until it clicked. My understanding of the language is more based on intuition (sheer memorization of exposure to it through cultural mediums) than on memorizing the grammar rules book. The brain makes the connections as to what seems correct or not based on patterns. I don't think my skills are good enough to write literature but surely communication isn't a problem.
Duolingo didn't exist at the time, but I believe it would have helped me learn faster considering the way it introduces languages is quite similar to how I started learning and it does so in a more interactive, fun manner.
* Can understand sentences and frequently used expressions related to areas of most immediate relevance (e.g. very basic personal and family information, shopping, local geography, employment).
* Can communicate in simple and routine tasks requiring a simple and direct exchange of information on familiar and routine matters.
* Can describe in simple terms aspects of their background, immediate environment and matters in areas of immediate need.
No way you need a tutor to get that. Duolingo course seems about right depending on language and language learning experience.
I have more recommendations if you want them.
More complex languages, yes, but for languages like swedish/norwegian/danish where there is very little grammar, I find it's much easier to progress within the limits of their program.
Swedish/Norwegian/Danish do not really have "little grammar", but for an English speaker, there probably won't be any need to explicitly learn the grammar, since it works mostly like English. But on the flipside, they are just as difficult as English for speakers of unrelated languages.
For a period in the UK there was no English grammar taught in schools. This caused me great problems in Russian class (second high school language) as I had no idea there were cases in English and so had no reference for why a case was needed and what it did. The entirety of my English grammar training was learning a poem by rote for homework, which I didn't do ("A nouns the name of anything [...]"). I learnt the little grammar I know from French lessons. So, YMMV depending on the English speaker.
Most English 'grammer' discussed in the Anglophone world (split infinitives WTF? English doesn't have infinitives) is gibberish...
I ran, she ran, he ran, they ran, we ran, y'all ran.
I run, she runs, he runs, they run, we run, y'all run.
I'll run, she'll run, he'll run, they'll run, we'll run, y'all'll run.
I thought I'd run, he thought he'd run, they thought they'd run.
We'll have wished we ran, they'll have wished they ran, he'll have wished he ran.
What exactly do you want to teach here? The only weirdness to the rule is that he and she runs with an "s", everything else is the same.
I love you. You love me. They love him. He loves them.
I want you. You want me. They want him. He wants them.
In Russian the above is far different because the word order can be switched for emphasis.
The only thing in English worth teaching is "I have" vs "I am" and almost every language has that same problem as well (Je suis vs J'ai in French).
The hard part with English is that our spelling makes zero sense, unlike Russian or French. The grammar is really quite straightforward.
Even verb morphology is a bit more complex than you've called out here.
To get to A2 you need a real tutor and real communication experience. I used Verbling to find a tutor and I traveled to Eastern Europe over the summer to practice and only after hundreds of hours of practice was I able to communicate in Russian to any degree even approaching A1.