anyone can take any meaning of the word 'strike'. it doesn't say anywhere in the quran that it has to be lightly. beating lightly with a toothbrush serves no purpose so it makes no sense to even have that ayat. and i find it very sexist that women are supposed to be disciplined by their husband.
And any one can take the meaning of prayer the way he wants. Does that mean everyone preys the way he wants ? No
You said beating lightly with a toothbrush serves no purpose.
Well if the purpose is inflicting pain, than you are right. There is no purpose.
However the purpose is not inflicting pain.
If someone came to me and said to me "we are in danger", I may have different reactions.
I may thing he is exaggerating it.
I may think we are in little danger.
I may think there is really a huge danger.
But if someone came, and shook my body and told me we are in danger, than I would understand that it is big. So establishing physical contact delivers the message more effectively. And we are talking about serious problem in the verse. It is marriage and divorce.
Anyways let's look back at the verse:
Men are in charge of women by [right of] what Allah has given one over the other and what they spend [for maintenance] from their wealth. So righteous women are devoutly obedient, guarding in [the husband's] absence what Allah would have them guard. But those [wives] from whom you fear arrogance - [first] advise them; [then if they persist], forsake them in bed; and [finally], strike them. But if they obey you [once more], seek no means against them. Indeed, Allah is ever Exalted and Grand.
So men are in charge of what? Of what Allah has given. It doesn't mean that you can do whatever you want like hitting her and make her do whatever you want because you will clearly see that women are honored in Islam.
Second they are also in charge financially which means they have to fully cover all house expenditures.
Let's also talk about the "strike" which is different form your understanding of the word.
Striking came out to be the third stage. The two previous stages are [first] advise them; [then if they persist], forsake them in bed.
Let us reflect on these verses by thinking of the situation.
The first stage was advising them. How much time would advising them take? A day or two? Ofcourse not. This is a serious problem, a first stage requires more time than that.
Stage 2 is [then if they persist], forsake them in bed. Similarly I think forsaking requires more time than a 1 week by logic.
Step 3 Is the striking [with a toothbrush].
However just because the striking is there, doesn't mean you have to strike. Read the verse which is after that. It says
4:35 And if you fear dissension between the two, send an arbitrator from his people and an arbitrator from her people. If they both desire reconciliation, Allah will cause it between them. Indeed, Allah is ever Knowing and Acquainted [with all things].
Therefore, you can go for the verse 4:35 to solve the problem. Just because it says strike them doesn't mean striking is for the purpose of inflicting pain. Neither does it mean you have to do it because you have to read the full context.