Korean Lilac Tree needs a severe pruning

Question

We have a Korean Lilac Tree (grafted onto a different trunk–we live in Canada).
Over the past 14 years, I think we haven’t taken enough off when we pruned, and one or two years we didn’t prune it.
The result is that it is getting too big–it’s slowing encroaching on our deck space.
There are only leaves on surface of the tree — like leaves only come on the newer growth each year, so if we trim too much, there will be no leaves (which is part of the reason we haven’t pruned it more heavily over the years).
So my question is, can we do something to get the size back under control or is it too late?
If we do a severe pruning, will the leaves come back this summer?
If necessary, we could do the severe pruning in the fall (thus forfeiting blooms for the next year)–we just really need to reduce it’s size — or replace it 🙁
Any advice you have is greatly appreciated!
Thank you.

Answer 1

You can do pruning, but only remove 1/3 of your shrub at any time.
Prune right after blooming.
Remove up to 1/3 of a branch to shape the shrub.
You can remove 1 or 2 of the older branches down to the base of the shrub to encourage new growth.
If branches are rubbing or are damaged, remove those.

https://www.gardeningknowhow.com/ornamental/shrubs/lilac/dwarf-lilac-varieties.htm