what's your opinion on the botvinnik system?


Your question is ambiguous. There's more than one system named after Botvinnik.
In the English Opening, you have the Botvinnik Pawn Structure, which is c4-d3-e4, but this is only effective when Black has played a reversed closed Sicilian structure. For example, after 1.c4 e5 2.g3 Nc6 3.Nc3 g6 4.Bg2 Bg7 5.d3 d6 6.e4 is fine. Black has many possible responses, like 6...f5, or other moves typical of the White side of a Closed Sicilian.
However, against the Symmetrical English, where the g7-Bishop isn't Blocked by Black's pawn, like 1.c4 c5 2.Nc3 Nc6 3.g3 g6 4.Bg2 Bg7 5.d3 and 6.e4 is total cr@p and White gets NOTHING!
Playing the English Opening requires massive flexibility. You have to be willing to also play either the Reti or transpose into QP openings. You can't rely on a single "system" against all lines of the English and expect success. If you aren't at least 2000 over the board, I'd suggest sticking with 1.e4 and 1.d4.
Next, there's the Botvinnik Variation of the Semi-Slav Defense: 1.d4 d5 2.c4 c6 3.Nf3 Nf6 4.Nc3 e6 5.Bg5 dxc4 (5...h6 would be the Moscow Variation). Here theory is extremely deep and you have to know it all precisely or you will get wiped off the board. I have won or drawn every time I've played this line as Black in over the board play, which granted I could count the number of times on my fingers, but all it takes is one minor slip-up and you are mince meat!
Lastly, there is the Botvinnik Variation of the Stonewall Dutch: 1.d4 f5 2.g3 Nf6 3.Bg2 e6 4.Nf3 d5 5.O-O O-O 6.c4 Be7 7.b3. The difference between this and the Modern Stonewall Dutch is Black would delay castling in favor of 5...Bd6 instead of putting the Bishop on e7, and always answering any c4 push with ...c6. The Botvinnik Variation of the Stonewall Dutch scores really well for White.

What is that supposed to mean?

Your question is ambiguous. There's more than one system named after Botvinnik.
In the English Opening, you have the Botvinnik Pawn Structure, which is c4-d3-e4, but this is only effective when Black has played a reversed closed Sicilian structure. For example, after 1.c4 e5 2.g3 Nc6 3.Nc3 g6 4.Bg2 Bg7 5.d3 d6 6.e4 is fine. Black has many possible responses, like 6...f5, or other moves typical of the White side of a Closed Sicilian.
However, against the Symmetrical English, where the g7-Bishop isn't Blocked by Black's pawn, like 1.c4 c5 2.Nc3 Nc6 3.g3 g6 4.Bg2 Bg7 5.d3 and 6.e4 is total cr@p and White gets NOTHING!
Playing the English Opening requires massive flexibility. You have to be willing to also play either the Reti or transpose into QP openings. You can't rely on a single "system" against all lines of the English and expect success. If you aren't at least 2000 over the board, I'd suggest sticking with 1.e4 and 1.d4.
Next, there's the Botvinnik Variation of the Semi-Slav Defense: 1.d4 d5 2.c4 c6 3.Nf3 Nf6 4.Nc3 e6 5.Bg5 dxc4 (5...h6 would be the Moscow Variation). Here theory is extremely deep and you have to know it all precisely or you will get wiped off the board. I have won or drawn every time I've played this line as Black in over the board play, which granted I could count the number of times on my fingers, but all it takes is one minor slip-up and you are mince meat!
Lastly, there is the Botvinnik Variation of the Stonewall Dutch: 1.d4 f5 2.g3 Nf6 3.Bg2 e6 4.Nf3 d5 5.O-O O-O 6.c4 Be7 7.b3. The difference between this and the Modern Stonewall Dutch is Black would delay castling in favor of 5...Bd6 instead of putting the Bishop on e7, and always answering any c4 push with ...c6. The Botvinnik Variation of the Stonewall Dutch scores really well for White.
Yeah, I was talking about the symmetrical. Didn't realize there was more than one. Thanks for the input, very descriptive and informative

First of all,
what's an opinion?

many (top) GM play it so it should give u an idea...
Many top GMs play it under given circumstances. Not as a catch-all system!
Do not confuse the fact that when amateurs ask these questions on here, they are often looking to use it as a blanket system against every response by Black. I've faced this structure over the board many times in circumstances where it's just terrible when facing lower rated opposition, like 1800 players.
For example, as mentioned in my previous post, it is often played against a Reversed Closed Sicilian setup with ...e5, ...d6, ...Nc6, and a Kingside Fianchetto by Black. It is not effective against setups where Black's g7-Bishop has open access to d4, and Marin is also of that belief (see his 1100 pages of English analysis across 3 books). I would make wagers that at the GM level, it is used significantly more often against ...e5 systems than against symmetrical systems. Does that mean it is "never" used by a GM in Symmetrical situations? Of course not, but also look at the situation at the time of the event. Does White only need a draw? Look at when they use it, not just the fact that they use it!

many (top) GM play it so it should give u an idea...
Many top GMs play it under given circumstances. Not as a catch-all system!
Do not confuse the fact that when amateurs ask these questions on here, they are often looking to use it as a blanket system against every response by Black. I've faced this structure over the board many times in circumstances where it's just terrible when facing lower rated opposition, like 1800 players.
For example, as mentioned in my previous post, it is often played against a Reversed Closed Sicilian setup with ...e5, ...d6, ...Nc6, and a Kingside Fianchetto by Black. It is not effective against setups where Black's g7-Bishop has open access to d4, and Marin is also of that belief (see his 1100 pages of English analysis across 3 books). I would make wagers that at the GM level, it is used significantly more often against ...e5 systems than against symmetrical systems. Does that mean it is "never" used by a GM in Symmetrical situations? Of course not, but also look at the situation at the time of the event. Does White only need a draw? Look at when they use it, not just the fact that they use it!
Alleluia...
What u say is rather true but is non sense for most club players, and more for players here who are mostly weaker than most club players.