The problem of slow Table Indexing after SQL Server Reconstruction

The database has been slow. I executed this statement two days ago to recreate all indexes. EXECsp_MSForEachTableALTERINDEXALLON? REBUILDWITH (PAD_INDEXOFF, STATISTICS_NORECOMPUTEOFF, ALLOW_ROW_LOCKSON, ALLOW_PAGE_LOCKSON, SORT_IN_TEMPDBOFF, ONLINEOFF)

The database has been slow. I executed this statement two days ago to recreate ALL indexes. EXEC sp_MSForEachTable 'alter INDEX ALL ON? Rebuild with (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON, SORT_IN_TEMPDB = OFF, ONLINE = OFF )'

The database has been slow. The statement was executed two days ago to recreate all indexes,

EXEC sp_MSForEachTable 'alter index all on? Rebuild (
PAD_INDEX = OFF,
STATISTICS_NORECOMPUTE = OFF,
ALLOW_ROW_LOCKS = ON,
ALLOW_PAGE_LOCKS = ON,
SORT_IN_TEMPDB = OFF,
ONLINE = OFF )'

Then, the database is shrunk, and the whole system suddenly becomes very slow. After the page is opened, the blank state cannot be loaded. There are many system users, and the server operating system is window server2008, I do not know whether it is related to IIS or whether it is necessary to re-index and shrink the database. What is the problem? Hope you can reply