If you read a litlle bit more on this excellent forum with lot of expertise from experienced caminhistas you can read that there is nothing wrong with the stages out of Porto.
Don't know who tells you that. They probably never walked out of Porto.
There are two first stages out of Porto
The Central way Yes the beginning is not so nice through the urban area but once direction the airport you will get into a more rural area.
Many here including myself advise to take the metro from the towncenter till Fórum Maia or Vilar do Pinheiro and walk from there. Nothing wrong with .Santiago gives his permission to do so from above.
The other stage is the coastal caminho along the Douro river and the ocean.
A beautiful and pleasant walk .
Once in Matosinhos you follow the wooden boardwalk with the ocean at your left
Nothing wrong with
In Vila do Conde you can make up your mind by choosing either the connection to the Central route in Arcos -we are talking about 12 kms. you even can follow an antique aquaduct for a while .all for free. I wished I had one here
Where I live.
You also can continue the coastal all away to Redondela where you will meet the central route to Santiago
Both paths are very well waymarked. All honour to the volontarios of Vialusitana who take care for the yellow waymarkers That may be said so we all can find our way to the shrine of the apostle.
So nothing to worry about . Just make your choice. The Porto metro is comfortable if you choose for plan A . Walking along the riverbank and the seaside -plan B is also great.
I did both during the years I walked the Portuguese and spent my holidays round Porto and the northern Douro and Minho region for many years .
This year -in one week from now by the way - I will take the metro to Vilar do Pinheiro and walk from there to Vairão where is the great albergue o Mosteiro do Vairão. Can't wait to be there.
Last year I walked the coastal to Caminha and followed the Minho river to Valença
Where our caminho ended . This year we first go to
Casa da Fernanda to enjoy the best albergue from the entire caminho Português and continue to Valença to acomplish the caminho from there to Santiago.
Wish you strenght by making up your mind.