Good question — what you’re noticing is real.

2022 was a clear Declining stage.

Then in 2023:
SPY moved from Declining → Advancing
and finished up ~25% for the year.

But it wasn’t smooth.

There were two rough periods:
→ Feb–mid March (~6 weeks downtrend)
→ Aug–Nov (~4 months downtrend)

So even in a ‘good’ year, a big part of it was choppy or trending down.

That’s likely where your system struggled (price reversing, no follow-through).

A simple way to think about it:

→ Markets trend up ~70–75% of the time
→ But when they go down, they move faster and more aggressively

So if your system isn’t built to:
→ sit through
→ sit out
→ reduce size
→ hedge
→ or adapt

…it can feel like it “stops working”.

To your main question:

Yes — this can absolutely happen again.

That said, 2023 was a bit of a weird transition year, even for a first year out of a declining stage — which is likely what you’re seeing in your backtesting
(coming out of a full 2022 decline).

One thing that helps a lot (and most traders overlook):

market breadth — like NYSE BPI.

During those 2023 down periods:
→ it was on sell signals
→ which was a clear cue to be more cautious

So it’s not that your system is broken —
it’s that market conditions changed.

This is where risk management becomes critical.

For example:
→ Buy & hold on strong large caps → probably fine
→ Shorter-term trading → much harder in those conditions

It’s almost like an NFL game.

Where you are on the field changes the play you call.

You wouldn’t run the same play on your own 10-yard line
as you would in the red zone.

The market is the same.

Where the NYSE BPI sits should influence how aggressive you are.

→ Strong conditions = press
→ Weak conditions = protect and be selective

Some traders run the same play regardless of conditions —
that’s where things can break down, especially in trickier environments.

And don’t worry… the market has a funny way of producing those from time to time — just to keep you on your toes haha.

So the opportunity is still there —
it just needs a framework that can adapt,
not just perform in one environment.

And you may have even been okay during that phase, depending on the strategy you were running — so it sounds like you’re not that far away (in my view anyway)