Blackjack Basic Strategy, played perfectly in a game with favorable rules, will reduce edge against you to about one half of one percent, best odds of any game in casino.
But still - it's a negative edge. While you can win in short term on any given day, in long term that one half percent edge against you will eventually grind you down if you play long enough and frequently enough.
An advanced basic strategy - or what we call Basic Strategy Plus - is necessary for you to step up from being a casual player to being a serious recreational player who has a better chance of winning over long term.
To reduce small edge against you with Basic Strategy even further, and at times even turn it into a positive edge in your favor, you simply must pay attention to cards on table and develop some sense of proportion of high cards versus low cards remaining in deck. This is exactly what a card counter does.
But you don't have to spend hundreds of hours it takes to become a proficient card counter. You can get a general sense of proportion of high versus low cards by doing something called "counting table". Counting table simply means that in any given hand, you look at exposed cards for all hands on table (including dealer's hand). Do a quick count of all high cards (tens, jacks, queens, kings) and all low cards (2 - 5). There are an equal number of these high and low cards.
If there are a much larger number of low cards showing than high cards (at least 6 more low cards than high cards in a six deck game), chances are that deck now is slightly richer in high cards, which is favorable for player. Conversely, if there are many more high cards showing than low cards (again, at least six more), chances are deck is now slightly richer in low cards, which is bad for player.